Lost Forever

"...we're not killing off any of the companions because everybody did. And then everybody cried... People test as they're playing the system and they go... 'I wonder if they're going to let me do this. Oh no! My healer is gone forever'!"

- Daniel Erickson on why Star Wars: The Old Republic is going to Avert this.

Also frequently referred to as being "missable," the dreaded Lost Forever is a game play component (such as an item, weapon, Sidequest, character, or plot event) that can become permanently inaccessible after a certain point in the game, therefore being "lost forever" if you miss them during the period in which they are available. A close relative and often an example of Guide Dang It. The bane of gamers everywhere, especially those shooting for 100% Completion, as it often forces them to start the entire game anew if they're not willing to accept a less-than-perfect run.

Lost Forevers frequently appear in areas that can only be accessed once, or are rendered unavailable after a certain plot event occurs. The early town that is destroyed, the mountainous area that caves in once you leave it, the village that you're banished from, the Load-Bearing Boss's hideout that goes boom after you beat it, the one-shot place that you're never given the option to return to, and so forth.

More rarely, things are completely random and arbitrary. For example, perhaps once you finish disc two and acquire the airship, the random shopkeeper you needed to talk to in order to acquire the Infinity+1 Sword suddenly closes up shop and disappears without explanation. Surprise! Guide Dang It.

Forgiving developers will sometimes provide an alternative means to reach what would otherwise be Lost Forever. However, reaching it with this second-chance method is usually much more time-consuming or difficult than if you had just gotten it the first time around. If a player knows such an item is coming, a common tactic is to save immediately beforehand, and restore repeatedly from that save until they manage to get it. This is often true when getting the Lost Forever is based on luck, such as when a boss Randomly Drops a unique piece of equipment.

This is infamously present in MMORPG's or any other game with online connectivity, due to one-time events, irreplaceable quest reward items (such as consumables that become Too Awesome to Use) distributed from an online source. While you can simply restart an offline game for another shot at the content, online Lost Forevers really can be lost forever. (When it comes to patch updates, however, players who still have the old items are usually allowed to keep them, and the items are often displayed as a badge of honor.)

Due to their tendency to induce great frustration, smart developers tend to avoid implementing these, and allow players to collect items or do sidequests at their leisure, whenever and in any order they want. Sometimes, this can result in silly situations where the player is presented with the option of returning to a location where there would be no logical reason to return to, such as, say, the site of a nuclear explosion. But, really, it's the lesser of the two evils.

Occasionally, a Lost Forever is intended to be just that: you get a one-shot item or spell that would completely unbalance the game if used elsewhere. You're not supposed to hang on to it, and the game either takes it away immediately or kills you if you try to run away with it. For some, the challenge then becomes cheating or glitching your way out of this restriction. Also see Guest Star Party Member.

Conversely, while most Lost Forevers are defined by the limited opportunity to acquire one, sometimes a particular item is acquired readily during a game's progress, but is irreplaceable once it is used up—should it get lost, stolen, or destroyed, you cannot acquire another one.

This trope is not to be confused with Final Death, where a character permanently dies and cannot be resurrected. If it's an item deliberately taken away from you, it may be Awesome but Temporary. If something vital to the plot becomes Lost Forever, the game is Unwinnable. Lost Forever should also not be a Point of No Return, where the game cuts off your access to prior areas. Chaos Emeralds can always be put in a Lost Forever situation since they are placed in Bonus Stages. Missable items tend to be found in a One-Time Dungeon.

Not to be confused with Ruined FOREVER!!!, although it can generate degrees of it.

Action Adventure

 * The freeware game Cave Story contains numerous easily missable one-shots, many of which are required in order to reach the secret hell level, which leads to the game's best ending. The worst of these moments: if you don't the ability to obtain the best ending are Lost Forever in one fell swoop.
 * To elaborate on getting the best ending: You'd naturally assume that you would want to . However, if you do that, two items necessary to get the best ending (and one necessary to ) are lost. Also, a little bit after that, there's a rest point that can easily be missed, as you are flying past it in a high-pressure stream of water. Even if you followed all of the other steps, if you don't you'll miss out on the best ending.
 * Not only can you not revisit the first two continents of Illusion of Gaia after you've left them, but you can miss some of the collectible red gems just by mildly progressing through the game a few steps - they just aren't there any more!
 * Also, one of the red jewels is accessible only in the first town, which isn't that bad except that it's randomly generated, and even then, still hidden making it a pain to find. If you're lucky, you may only have to enter and leave the seaside cave where you meet your friends a few times. Often, however, you have to do it close to 100 times before the fisherman appears at the other end of the dock with the bottle (containing the Red Jewel). Most people, naturally, never even know it's there.
 * And this doesn't even begin to describe the rare and easy-to-miss herbs. There are only a small number of them in the whole game, and you naturally use them when you get low on health. Don't. You'll need them to fight the Bonus Boss.
 * One of the most fun side quests in Terranigma is expanding the towns, but watch out! If you vote for the conservative candidate in Loire, the town will never progress to the next stage. And if you lie to Bell about his girlfriend, he'll never invent the telephone and Freedom will be left in the dark ages. To make things even worse, not upgrading those towns means that Nirlake and Suncoast will never be able to progress, either!
 * In it you can also lose  potentially costing you... well not much really, just a Majirock and an easter egg.
 * Furthermore, there are two islands in the game (Polynesia and Mu), which only appear if you've completed two entirely optional and missable side-areas in the first chapter of the game. If you never completed said area's objectives before the game's first chapter is finished, the islands will never appear on the World Map, and whatever items and treasures were waiting for you on said islands will never be accessible.
 * The Legend of Zelda games are by and large aversions of this trope—Miyamoto has actually said in an interview that he always tries to avoid Lost Forever and Unwinnable scenarios in his games.
 * A glitch causes one opportunity to upgrade Deku Nuts in Ocarina of Time's Lost Woods to be rendered Lost Forever once the player obtains the Poacher's Saw, an item in the future era's trading sequence. This glitch is removed in the 3DS remake.
 * Meanwhile, in the original Legend of Zelda a couple of old men would give you your choice of either a Heart Container or a Red Potion. If you choose the Potion, the Heart Container becomes Lost Forever.
 * Similarly, the Nintendo Hard second quest has rooms in certain dungeons that require you to leave 50 Rupees or one of your Heart Containers to proceed. If you don't have the cash, one of your Hearts is gone for good.
 * Although The Wind Waker didn't have any permanently missable items that mattered, if you wanted to achieve 100% Completion on your pictography you needed to take a pictograph of everyone alive within the game; enemy, ally, NPC and boss alike. This is alleviated somewhat by the New Game+ and the Boss Rush near Ganon's Tower near the end of the game, but it's difficult to get a photo op of certain subjects (like a random Rito NPC that inexplicably disappears after a plot event), so they can eventually become Lost Forever anyway.
 * The Minish Cap features this trope for the Light Arrows, which can only be found if the player "kinfuses" with a seemingly random, arbitrary person to unlock a teleporter that leads to a location later in the game, where they must, who gives you the arrows. Otherwise, by the time you can reach said location normally   and the item is lost.
 * In Twilight Princess, you must collect the wooden Ordon Shield before Midna will take you back into the Twilight-covered Faron Woods. Should the shield gets burned up by fire, you can only replace it with the plain Wooden Shield from shops, which is functionally identical but lacks the Ordon Shield's unique goat-horns design.
 * Didn't have a D Si or 3DS to download The Legend of Zelda Four Swords: Anniversary Edition onto before February 20, 2012? The entire game is Lost Forever to you unless you buy a used handheld with it already downloaded.
 * Beyond Good and Evil has a particularly irritating example - the final animal that you need to photograph is a Space Whale hidden in an asteroid you need to shoot while on your way from Hillys to the moon. If you get to the moon without destroying the asteroid and photographing the space whale, you lose the photo of the space whale forever, because your space engine stops working once you reach the moon.
 * This game actually goes out of its way to avert Lost Forever, especially with animals—even bosses have second chances to photograph them, usually by going back to their respective arenas. However, there is one that becomes, if not lost forever, difficult to acquire to the point of being meaningless. The Sarcophagus DomZ are fought exactly four times during the course of the game, and they don't respawn. The first time is in the intro, before you even have a camera. If you miss them the second and third times they spawn, they still appear once more—but only during the final boss battle. Which you can't save after (there's no Playable Epilogue), so the cool prize you get for getting all the animals (a catalogue of all your animal photographs) is totally useless.
 * Also, if you don't get Pey'j's boots while in the factory, you have no way of knowing.
 * In Okami, in order to achieve 100% completion, you must find and feed every animal (or cluster thereof) in Nippon. Of the hundred or so animals that litter the game, one is missable, which is found during a one-time trip 100 years into the past. If you forgot to feed that one dog, you won't get another chance.
 * Any clover in the Moon Cave, Oni Island, The Emperor's Palace or through the Spirit Gate, although their only rewards are Praise.
 * The unripened fruit on the sapling in North Ryoshima must be gotten with the help of the archer who will permanently leave the area after a certain point. It only contains Praise though, making it effectively just another clover.
 * Fire and Ice Doom Mirrors inhabit one specific room in the one-time Emperor's Palace. Unlike most enemies, the Doom Mirror family is exclusive to this area, so if you prefer to avoid demon battles then these bestiary entries are Lost Forever. Thankfully they can be gotten in the New Game+.
 * Thankfully averted with the Fishing minigame. If you progress far enough, the Agata forest fishing spot becomes unavailable, but it is replaced by a new fishing spot near the Imperial Palace in Sei-an City, which contains the same species of fish.
 * Castlevania: Dawn of Sorrow has the Chaos Ring, which increases your MP regeneration rate so much that it effectively gives you unlimited magic. To get it, you need to possess every soul in the game, including one-of-a-kind boss souls. This wouldn't be so bad (as said bosses are guaranteed to drop their souls), but if you use these unique souls to synthesize more powerful weapons, the Chaos Ring cannot be collected. Thank God for New Game+...
 * The same ring is a pain in Aria of Sorrow, but for a different reason. You can't miss a boss soul in Dawn, but in Aria, there's exactly one you can miss—and it's easy to do. You must destroy Legion's entire shell before killing him if you want his soul. Again, New Game+ is your best recourse if you miss it.
 * Portrait of Ruin has the same item, and the same problem. To got the ring, you must complete all of Eric's quests. However, many of them require you to gather specific items of which there are only one in the game. Thankfully, there is a new game + option. But really, who would have guessed that that Longsword you probably sold within an hour of getting would be necessary to complete a quest later on? Or that that there is only one Longsword in the entire game?
 * There's also the ability to buy items from other players via Wifi. It's telling that you are more likely to find a store selling thick glasses, amanita mushrooms and nun's clothing than a store selling the best weapons and armor in the game.
 * And Order of Ecclesia maintains the dubious tradition! This time you're collecting glyphs (basically the same as souls), and two of them come from bosses. The Globus glyph can be grabbed from a regular enemy later, but if you fail to grab Acerbatus in the battle with Albus, you'll never get another shot.
 * In Circle of the Moon, there's a secret item crush accessed by using the DSS technique with no subweapon equipped and at least 100 Hearts in reserve. Since you can't unequip subweapons after the first time you pick one up, this technique is easily Lost Forever. Combined with the other requirements, it's also Awesome but Impractical.
 * The PSX version of Harry Potter and the Philosopher's Stone is downright brutal to anyone trying to get 100% completion. Certain wizard cards can only be obtained by getting a perfect score on a certain minigame. But you have to try again and again until you get the card, without stopping, or else the door locks itself as you exit. So much for that card, eh? Luckily, the PSX version of Chamber of Secrets averts this entirely by letting you go back to places once you lose access to them.
 * Actually, the Knockback Jinx upgrade in Chamber of Secrets can only be obtained near the end of the game, but go too far and it's Lost Forever, AND you can't get 100% completion. Ironically, when you get the upgrade, a speech glitch occurs. Perhaps EA planned on removing it?
 * This is also true of the PC version of Philosopher's Stone; treasure chests containing certain cards or other items are available only at certain times and cannot be recovered later. Chamber of Secrets was much more forgiving in this regard.
 * The PC version of Philosopher's Stone primarily had this as a symptom of its extreme linearity; the game progressed one-way in levels, and you couldn't go back to previous levels (in many cases, you couldn't even go back one room within the same level) leaving absolutely no margin for error regarding things like house points or wizard cards. The cards you care about; the points don't even do anything in-game. Chamber of Secrets allowed you to replay any spell challenges for more house points or to obtain wizard cards, and essentially had much of the game take place in a massive hub, where most wizard cards were in the hub itself; quidditch matches were also replayable to increase house points gained, and any time you went through an area you couldn't go back to, any wizard cards you missed went into shopkeeper circulation, allowing you to purchase them at your leisure. Granted, quidditch matches were more fun in Philosopher's Stone, when you could fly anywhere you wanted to on the pitch; Chamber of Secrets stuck you on a rail where you had to maintain speed while smacking around the opposing Seeker.
 * In the NSTC version of Sphinx and the Cursed Mummy, one of the monsters necessary for the Collection Sidequest, the Smiling Burble, can easily become Lost Forever. It only appears twice: The first time, it's part of a Multi Mook Melee that you can't replay, although three of them appear at once. The second time, it's in a tiny nook in one portion of a late-game dungeon, and if defeated, the monster that appears there does not respawn. If you don't catch it during one of these appearances, you won't be able to, and thus can't get 100% Completion. The PAL version, however, has the monster in the late dungeon respawn.
 * In Brave Fencer Musashi, a longevity berry can be missed if you didn't talk to the mayor after saving Steamwood. You won't receive the berry from the mayor after chapter 2 preventing you from getting max hp.
 * You are given only one shot at obtaining either of the two whip upgrades in La-Mulana. The upgrade in the Inferno Cavern can be sealed off by two rising stone pillars, and the entrance to the upgrade in the Tower of the Goddess permanently seals off behind you once you enter it. Additionally, the penultimate area, the Shrine of the Mother, will disappear forever along with any items you missed in there (most notably the final life upgrade) after all eight bosses are defeated.
 * The Life Jewel in the Dimensional Corridor can be easily made not Lost Forever, but difficult to get to if you defeated the miniboss before you went up to the Life Jewel's location. It's possible, but very difficult to do, to get it after killing the miniboss, but it requires using the knockback from the enemies. Also, the Angel Shield (in the Dimensional Corridor, again) can be lost forever if you only have 1-2 minibosses left, and if you hit the wrong face in the Temple of Moonlight, the elevator that leads to the Axe will be blocked off.
 * Hell Temple is also permanently sealed off if you screw up the unlocking process, which is quite easy to do. Given the general nature of Hell Temple, though, this is probably something of an act of mercy.
 * The Tower of Druaga is really evil about this. Guide Dang It if you don't know how to get the treasure on a floor (while paying mind to the time limit), but if you don't you might not be able to get some later, necessary treasure.
 * Prior to version 1.3 of Project Starfighter, selling your secondary weapon caused you to have no secondary weapon at all. Since the plain rocket weapon cannot be bought, this meant you couldn't get it back once you got a new secondary weapon to replace it.

Adventure Game
""The plant's gone. I'm stuck up here!""
 * Should you find yourself at the very beginning of the old Infocom The Hitchhikers Guide to The Galaxy game, you will want to get the toothbrush. It's not the only thing you'll need from that first stage, either. Once Earth's destroyed, of course, you're sunk.
 * ">get all" is your friend.
 * Similarly, when you're in the Vogon ship, if you don't manage to get the Babel Fish before the Guard drags you away, you might as well quit and restart now, all that happens next is a lengthy lead up to Game Over.
 * Sadly, many people don't realize the * reason* you need the Babel Fish is to get the atomic vector plotter. You only have a few turns to grab it, too, and in a particular twist of evil the thing your aunt gave you that you don't know what it is is likely to have reappeared in your inventory, making your load too heavy to pick it up, forcing you to waste a turn dropping the thing.
 * Really, every Infocom game ever embodies this trope pretty much.
 * Hotel Dusk: Room 215 features a sidequest in which you can earn a prize from a vending machine. There is only one very short point in the game in which you can exchange your cash for change; after that, it's lost forever. (There is also no warning, making it a Guide Dang It.)
 * There is a kind-of new game plus mode after completing the game with an extra puzzle and ending, but the scavenger hunt item you get out of the machine changes, making the original Lost Forever unless you start a clean game. In addition, the original scavenger hunt vending item can be given to two different characters, but the only way to give it to one of them is to randomly guess the vending machine number, because there is no opportunity to give it to her after legitimately completing the scavenger hunt.
 * The text-based game of The Hobbit required Bilbo to get assistance frequently from either Gandalf or Thorin—most notably, getting out of the goblins' dungeon (you had to be carried out the window) and getting into Smaug's cave via the side entrance (the key broke if Thorin died). The game also depended on the elves' butler to periodically open the door to the wood elves' dungeon. If these parties were killed, various areas became unreachable, and randomly spawning enemies like goblins and the vicious warg often killed them while Bilbo was elsewhere.
 * Return to Zork. Most notoriously, if you cut instead of dig up the bonding plant at the very beginning of the game, killing it, you're screwed. Even worse, it's very late in the game when you find this out. Additionally, there are many ways of killing it by accident if you do dig it up.
 * Likewise, the earlier text game Spellbreaker had a plant that you needed to dig up rather than cut to solve a puzzle. And just to make sure as many people as possible found that out too late, the game placed a Red Herring pair of shears near the plant.
 * In Maniac Mansion, pouring film developer on the Man-Eating Plant will kill it, preventing you from climbing into the observatory for the rest of the game. If a character is up there when the plant keels over:


 * Gabriel Knight: The Beast Within is a huge point-and-click game, six discs large. If you forget to pick up a certain item in the chapter on disc two, you will get stuck at the end of the chapter on disc four.
 * In King's Quest V, there is moment where you MUST throw a boot at a cat chasing a rat, so that when your character is trapped later, the grateful rat will free you. The cat-and-rat chase moment happens quickly, and the game gives no obvious cues that you must throw the boot. If you don't, your character will not be freed, thus culminating in a game over.
 * All of the old Sierra adventures had this feature. Forget to get the rabbit before leaving the first scene in Space Quest IV? It's a shame you won't need it until the end of the game. Didn't notice the oil-eating bacteria at the start of EcoQuest? Guess you're plum out of luck. Need one go on?
 * Luigi's Mansion features both golden mice and blue ghosts. Blue ghosts appear in the blink of an eye in certain dark rooms and vanish just as quickly; if you don't catch them in one go, they'll vanish forever. Golden mice are similar, but instead of just vanishing, they move really quickly, and can be vacuumed up in one hit. Both types will disappear if you turn all the lights in the room on (by defeating all the other ghosts) first. Both of them drop the same thing: Lots and lots of money, and, in the case of the blue ghosts, gems.
 * It also has a plant in the Bone Yard that can be watered after every chapter. Miss it once, and the plant dies, meaning you lose the chance to get one of the giant diamonds worth a lot of money, and a huge amount of assorted coins and bank notes.
 * Myst and Riven are very hard to make Unwinnable. But ''Myst 3: Exile" has a snag quite late in the game: if you get the sequence of actions wrong when you confront Saavedro, he'll toss the Releeshan book off a cliff... and you'll never get it back.

Card Battle Game

 * Nightmare Troubadour for the DS features an accidental example due to a glitch in some versions of the game: after beating Marik, the chance to duel Pegasus is lost forever, along with the chance to trade with him for the one-of-a-kind Imperial Order card. At one point there was a giveaway that would put the card on your game, but that is most likely over now.
 * In Digimon: Digital Card Battle for the PSX, you get to choose a partner Digimon at the very start of the game, and you get two more later in the story. What nobody told you is that you have to choose them from a pool of 6, and that the decisions are permanent; the three partners you didn't choose are lost forever unless you cheat. That means that if you chose V-mon, Patamon and Tailmon/Gatomon (depending on the localization) and you were later aiming to get Wormmon, well, sucks to be you. At least the programmers had the courtesy of letting the player use "Borrowed decks" from people to get a chance of getting the card data of the partner Digimon you didn't choose, and their respective Armor Evolution data. Not that it's explicitly stated by anybody on the game, though...

Driving Game

 * Anything related to Norahike in Choro Q HG4 after This includes loads of synthesis parts obtained from him which require you to spam on entering his house until you get everything.

Edutainment Game

 * In the bizarre spinoff to Oregon Trail called The Amazon Trail, you can catch a pirarucu, a fish that's as long as a bus in the Fishing Minigame. It only swims by once, but it takes up half the screen and if you don't catch it, that's your problem.

Fighting Game

 * Mortal Kombat: Deception has a chest with one of its unlockable fighters, Kenshi, in the small village where your character begins the game as a child. Leaving the village causes your character to grow older, so the game prevents temporal anomalies by locking you out once you've left. If you leave before finding the chest containing the Kenshi unlock, it will be Lost Forever - the only way to get it is to start a new save file.

First-Person Shooter

 * Borderlands has the Rider, a fairly standard scopeless sniper rifle. The gun itself is a reference to A Christmas Story, both in its similarity in appearance to the BB gun Ralphie wanted for Christmas, and to the spoiler text -- "Careful... you might put someone's eye out" -- which is a quote from the movie. It can be found in a hidden basement in New Haven, the entrance to which is only unlocked while a single mission -- —is active. Once the Vault Key piece is picked up, the door to the hidden basement locks again, and the Rider is lost.
 * An interesting point of note is that the flavor text of the gun is a subtle hint regarding the giant Rakk Hive you have to kill in order to pick up the Vault Key piece.
 * In Metroid Prime, many of the scans become unavailable after a certain point. The two most notable examples are anything on the wrecked ship at the game's beginning, and the Ice Shriekbats (fixed in the PAL version), the one type of enemy that doesn't respawn (and that has the tendency to kamikaze into you, just to raise the frustration factor). In addition, all bosses must be scanned during the fight—you won't get the chance again. That said, the Hard level allows some missable enemies to be found in other places other than their original rooms (from which they vanish after a certain point).
 * Metroid Prime 2: Echoes continues this dubious tradition. A particularly nasty scan is the special door lock that appears during only one fight; you have to take your attention off the enemy to even notice it. One boss has five separate scans. Even Samus's ship is a missable scan—the scan data changes as repairs progress.
 * Naturally Metroid Prime 3: Corruption changes none of this. And hey, look! Another limited-scan Shriekbat! At least that game allows you to carry over your scans into a New Game+ so you have another shot.
 * How about your three fellow bounty hunters ? You get a total of two attempts at scanning Ghor, and a single shot at scanning the other two. Naturally, the only time you can scan all three other hunters at the same time is during the first Timed Mission, and if you flub this chance, then your options are to either reload your game or soldier on through for that New Game+.
 * Concerning a New Game+, there are also missable scans on the final planet. The fun part: You take damage over time, so if you play on harder settings and are struggling as is, you don't really have the time to scan everything.
 * All three games feature the ability to keep your logs with the New Game+ in the Metroid Prime Trilogy pack.
 * In Metroid Prime: Hunters there is a type of voldrun that is missable. It only shows up in one room, and is the only type of voldrun that does not respawn when you reenter the room. There's also the fact that it looks almost exactly the same as every other voldrun in the game.
 * In Half-Life 2: Episode 2, in the beginning of the game, Gordon and Alyx are stopped in a communications shack talking to the headquarters of the resistance. Underneath a shelf next to the locked exit door is a gnome. If you pick up the gnome and take it with you, all through the game, at the end, if you place it into the rocket, you get an achievement unlock. The Gnome never appears any other place in the entire game, and if you don't get it in that shack, you can never get it again.
 * The gnome later appeared in the Dark Carnival campaign for Left 4 Dead 2. You also got an achievement when you brought it to the end. Noticing a pattern here... It also leads to some funny moments, as you have to win a shooting gallery while being attacked by hordes of zombies to get it, and whoever's carrying it is mostly defenseless. It leads to some funny voice-chat comms, too. "Protect the holy gnomecarrier!"
 * Brought up again in two mutation modes, Last Gnome on Earth and Healing Gnome. Both modes require you to carry the gnome from start to finish (on any map, not just Dark Carnival this time) and you can't advance to the next level without the gnome in your hands. If the gnome gets tossed over a fence or left behind a Point of No Return, the game is then Unwinnable
 * This might be a shout out to System Shock 2. In the training mission (before you pick your class etc.) you can find a basketball. If you pick it up, it will stay with in your inventory to the actual game (in between of which there is a three year training period, mind you :)). If you keep it with you all the way up to the recreational sector of the ship (very far into the game), you can throw it into a hoop. You then recieve a secret prize.
 * There are five audio diaries in BioShock (series) in two areas that you cannot backtrack to.
 * Bioshock 2 has you collecting research information on enemies in exchange for unique character abilities. The early Mook enemies stop spawning once you're strong enough, so if you haven't maxed out their Research Track, say goodbye to their bonus and the One Hundred Percent Completion achievement for Research.
 * Given the finite amount of ADAM one can receive in any given playthrough, certain Plasmids, Gene Tonics and Upgrades can be Lost Forever if you did not purchase them before your ADAM ran out. Likewise, there are only a limited number of Power to the People Vending Machines in the game, which is less than how many times you can upgrade each weapon in total (each Power to the People will be permanently deactivated when you use them). On top of that, if you Kill Sander Cohen, one of these limited machines will also be Lost Forever, further limiting your upgrades.
 * Considering you can't backtrack between levels at all in BioShock (series) 2, any audio diaries you haven't collected when you advance to the next level become this.
 * In Quake, it's a given that you can't backtrack to previous levels. However, maps E4M4 and E4M5 have a message saying you forgot something important if you didn't pickup a certain weapon on that level. This would imply that it would be lost forever, but the following levels contains the weapons you skipped past. To trigger those message, you're likely going out of your way to skip them.
 * Team Fortress 2 gave users the ability to permanently delete unlocked weapons. For a brief period, players were panicking over the prospects of not being able to re-unlock these weapons, because they were tied to achievements whose records were stored on Valve's servers—in other words, those achievements could not be manually cleared. Then Valve introduced their new Randomly Drops system of attaining unlockables, and not only could players breathe easily, but suddenly being able to delete duplicate items became VERY important.
 * A give-away for unique medals for the Soldier class was held on a first-come first-serve basis. If you missed the giveaway there is no other way to get a medal for your Soldier.
 * Valve rewarded all player who didn't use external idling programmes to gain unlockables with a halo that no one who used an idling progamme or didn't already have the game when this was given out can get.
 * Somewhat subverted with the Mildly Disturbing Halloween Mask and the Ghastly Gibus. The former was only attainable during the Halloween event by picking up 20 treat drops from dead players, but there is a high chance that said event will be an annual event, making the hat attainable once again next year. The Ghastly Gibus on the other hand was attainable the same way as the Gentle Manne's Service Medal, through a secret page. However, it can be attained by gaining an achievement which involved dominating a player that has said hat equipped at the domination. Unlike the Mildly Disturbing Halloween Mask, it can also be attained even when the Halloween event is not active.
 * The Gibus has become a weird moving-target example of this; it can still be obtained in its basic form at any time by dominating a player who's wearing it, but each Halloween, the existing Gibuses get "upgraded" in name and appearance. Currently there are 3 levels of Gibus: Ghastly (1), Ghastlier (2), and the highly confusing "Ghastlierest" (3). Newborn Gibuses start at the first level and will reach the third level two Halloweens later, but by then the level 3 ones will be level 5; the highest-level Gibuses, whatever they are currently called, will always be Lost Forever.
 * Valve also likes to give away items based on when you buy OTHER games. For example, the only way to get Bill's Hat was to pre-order Left 4 Dead 2 and the only way to get the Big Kill, the Lugermorph, and Max's Severed Head was to pre-order The Devil's Playhouse or buy it the first week it came out. Poker Night At the Inventory gives you a second chance to get The Lugermorph.
 * Introduced in the lead-up to the Engineer Update was the Golden Wrench. Basically, in order to get it, you had to wait for a specific time for the opportunity to open, and then you have a one out of a hundred chance to get it... by crafting. There are only 100 Golden Wrenches in total. However, for each 25 Golden Wrenches, part of the Engineer update was revealed.
 * Doom II has a level (MAP 27: Monster Condo) with an area which sneakily seals itself off 30 seconds after the level starts, and is thereafter totally inaccessible (it can be opened only from the inside). It's not too far away from the start point, but unless you know about this sector beforehand there's absolutely no way you'd find it in a normal play through the level. What's worse is that it's a marked Secret Area, so it affects the score on the intermission screen; if you get to the area too slow, you're not getting 100% secrets.
 * In Descent II, some secrets are only accessible by one-shot timed doors or become blocked off by Mobile Maze barriers. If the door closes, fugeddaboudit.
 * In Call of Cthulhu (tabletop game): Dark Corners of the Earth, the refinery contains a sniper rifle, but it's hidden behind a door in an office you pass through. If you do not close the door behind yourself and take the rifle when you first enter the room, it will be Lost Forever, as you cannot return to the office once you leave it. What's worse, getting this rifle is necessary for a 100% Completion... which is the only way to see the proper ending and make sense of the plot.
 * In Red Faction: Guerrilla, the most useful vehicles are the Walker mechs. Because they're so perfect for destroying things, you will almost never see them outside of the specific missions where you use one. There are a few places where you can find a Walker, unless you destroyed the building that was there. In the unlikely event that you either just happened not to destroy the building where one of the Walkers might spawn, or you knew beforehand not to destroy that building, you could very well see a Walker there. Most of these buildings are EDF property which you are encouraged to demolish, and if the building is gone, you can't get a Walker from there anymore.
 * Killing Floor has added a few promotional playermodels, only obtainable by preordering another game (such as the protagonist of The Ball) or unlocking a specific number of achievements during an event (10 of 13 summer achievements to unlock a Steampunk version of Mr. Foster); when the game is released or the event ends, you can no longer get the models.
 * In Oddworld: Stranger's Wrath, we have the Binoculars, which are only available at the General Store in Gizzard's Gulch (right at the start of the game), and said General Store gets destroyed in the battle with Boilz Booty. Didn't buy the Binoculars? Well then, you won't be able to use the game's Sniper Rifle equivalent, the Sniper Wasps, as they can only be accessed/used through the Binoculars. This is mentioned nowhere.

General

 * In games featuring a magic system that involves getting enemies' skills (such as Final Fantasy's Blue Magic), there will often be spells that can only be learned from bosses. Kill them without learning the spell, and it's Lost Forever.
 * Arguably, games that use achievements that are tied to online play can fall under this. Game servers are not kept up forever and if you didn't get any achievements based on an online action when the severs are shut down for good, the achievement will never be unlocked. This gets worse if the achievement requires an action from another player and they keep doing things to prevent you from getting the achievement. For example, Left 4 Dead 2 has Strength in Numbers, which is unlocked by starting a Team VS/Scavenge game and winning. Since the game is known for having people Rage Quit all the time, many people will probably never get this achievement.

Hack and Slash

 * The developers of Diablo III are considering introducing a setpiece revolving around a collapsing dungeon full of treasure that players have to make a decision on whether to run and save themselves or collect the loot and potentially die. Given the random nature of the game, whatever items are in the dungeon will probably be lost if not picked up then. Please, somebody stop them.
 * Considering that all loot in the Diablo series is randomly generated, any items that get lost when the tomb collapses could probably be found anywhere else. Based on experience with the actual dungeon at Blizzcon, the true value was that the tomb was extremely abundant in Resplendant Chests (like, 2 in every room), which are guaranteed to drop a rare item and 2-5 magic items. Plus everything resets when you quit and come back, so you have a chance to go again if the entrance randomly appears.
 * In the majority of Hack and Slash games with a Random Number God, any piece of gear with a specific combination of stats can be considered Lost Forever if the player fails to notice it while sifting through Vendor Trash or accidentally gets rid of it, due to the chances of the same stat rolls lining up being less than one-in-a-million. Wonder why hacking is so attractive in online play?

MMORPGs

 * Many Free to Play MMORPGs give exclusive items to participants in each of the game's beta stages (pre-release beta stages, that is, usually Closed, Open and/or Invitation Only stages) to honor their participation and as a partial compensation for the necessity of wiping their hard-built characters before opening day. Those joining after the official release naturally can't ever obtain them unless the service provider distributes them for new channel or expansion betas.
 * A Final Fantasy XI example: There are actually quite a few items you can only get once, and worse, they can't be sold or traded to other players, so you can save space on your character-that-can-do-anything. Most of these aren't exactly that good, but then you have examples like the Bibiki Seashell, a very decent tanking item... that once could be accidentally thrown, before a patch fixed it.
 * Final Fantasy XI's Game Masters will generally restore one item you accidentally lose. Needless to say, this ability is Too Awesome to Use for most people.
 * The MMORPG City of Heroes has the anniversary badges. If the character wasn't around for the anniversaries, there's no possible way to get the badge.
 * There is also the "Efficiency Expert" badge in City of Villains. To get it you must successfully complete all but one of Pither's timed missions, if you fail more than one then you'll never get the badge. Not even if you have a friend get the missions and do them with him. None of the missions are available via the flashback system either.
 * If you fail any number of missions, you can still get the badge by abandoning the completed mission. When you abandon a mission (not to be confused with auto-completing it), it drops from your list of missions, and talking to the contact gives the mission you just abandoned for another try. But of course, you can't abandon a completed mission... unless you're a Rogue and go to any of the Paragon City zones, which will automatically abandon all your missions, no matter what state they're in.
 * The Gold Magnate ship in MMORPG EVE Online is an extreme case. Only one such ship was given out as an event prize. It was eventually destroyed in PvP combat, making it well and truly Lost Forever.
 * While the Gold Magnate is the only unique ship in EVE Online, there are a number of other ships produced in such limited numbers that they are close to being Lost Forever. The Silver Magnates, the Guardian-Vexors and the ultra-faction battleships are not in production and are therefore ultra-rare collectors items, several of which have fallen into the hands of a certain famous collector. Pirates in EVE leap at the chance to destroy anything unique.
 * World of Warcraft has a variation of this: Some specific quest rewards are items that you can only get this one way. Use it or sell it, and it's Lost Forever for that character. And some of these quests are only available to one faction... Of course, those limitations also make them Too Awesome to Use.
 * And of course, when you choose a reward for a non-repeatable quest the other possible rewards for that quest are Lost Forever for the character.
 * After the expansion came out, a certain world boss moved to a new location, got a level upgrade, and dropped new loot. Unfortunately, this caused all of his old loot to disappear, save for one item that could also rarely be found on more common enemies.
 * And the next expansion did it again, relocating and retuning an old dungeon.. sans one Infinity Plus One Staff. Also, many mounts and titles are Lost Forever if you weren't playing the game during a specific timeframe. If you started playing just recently.. sucks to be you.
 * Players who acquired these items when available received the corresponding Feat of Strength achievement.
 * Another of WoW's many examples of this are the classic PvP ranks. Originally, players could gain (and lose) one of 14 ranks, ranging from Private/Scout to Grand Marshall/High Warlord, based on their PvP performance on a week to week basis. In addition to rewards which became available at each rank, players also received the associated title before their name. With the release of the Burning Crusade expansion, this ranking system was scrapped, and while the item rewards were made available through other means, the titles can no longer be gained by players. Those players who had earned a title before their removal are given the option to display it, and players who still have their title often wear it as a sign of veterancy and badge of honor.
 * These will be returning in Cataclysm as part of the rated BG feature, making it possible other lost items/additions can return at some point too.
 * In addition, the game's achievement system has a tendency to award titles/vanity pets/mounts/etc. with the completion of its harder and/or obnoxious requests. The most significant examples of this are the prestige mounts awarded for being within a certain upper percentile of the PvP arena rankings for a particular season, and/or by finishing all the "hard mode" meta-achievements for each content patch's PvE raid content - during that patch's duration. You see, the mount (and in some cases, title) rewards are removed when a new content patch rolls around, under the belief that the increasingly powerful gear provided by each would result in an immediate brute-forcing of those missions. This ensures that said rewards are badges of honor for PvE / PvP superstars.
 * Probably the most infamous example would be the unarmored epic ground mounts. Patch 1.4, released a few months after the game was released, replaced the original epic ground mounts with the new, armored models. For a player to have an unarmored model today, they have to have earned 1000 gold before the patch replaced them, a very difficult feat. Pity, too, because Ivory Raptor is one of the coolest mounts in the game.
 * With the Cataclysm expansion, many NPCs and landmarks from the original WoW were wiped off the map by the expansion's Big Bad, along with their associated quests. In a variation of this trope, new quests dealing with the aftermath were added.
 * Kingdom of Loathing has many items and rewards that cannot be acquired anymore. It's not a game for completists.
 * It's also notable that they give consolation prizes constantly to the most dedicated completists, if only because they frequently give away special items to extremely helpful players or members of the dev team as well. Two such members dismantled their Completist status by DESTROYING their unique items to find out what they became, as the prize for doing so to ultra-rares is an Ultimate Wad, an instant level up. They became useless powders instead. Furthermore, when a third player who currently had the pulverize ability was awarded a special unique reward item (for being the first to pulverize an ultra-rare), they lampshaded and averted this by making said item pulverize...right back into its original state. Yes, that's right, the urge to break things actually wins out over 100% Completion in this game a lot of the time, even with Completists, meaning numerous gift items shall never return, unless the admins wish it so. Also some trophies are awarded on a lark, such as the infamous 2006 pantsless trophy. If you had pants on at rollover on New Year's, you didn't get it. Furthermore, if you weren't watching the in-game chat at the time, you had no forewarning.
 * In the original Guild Wars, the beautiful tutorial area is irreversibly destroyed in an event called the Searing, turning it into a desolate wasteland. Thus, once your character goes through the searing, you can never return to the tutorial (which has become known as presearing, and the rise of "permapre" characters who choose never to sear). Getting to max level in presearing awards a special title.
 * Another fun thing from the tutorial was a special item that the little girl Gwen gave you. It didn't do anything. Even if you finished the game, there was no use for it, as Gwen was never found, and it was taking up space in your inventory. After some 3 real-life years, the 3rd expansion came out, and Gwen was there. Anyone who had saved the item could now use it for a bonus quest/item. For everyone else: Make a new character.
 * Then there're the lost riches of the duping scandal. In 2007, a bunch of players figured out how to manipulate a new mechanic in order to dupe items. Naturally, they started producing mass quantities of Armbraces of Truth (a high-end item that could be traded in to collector NPCs for rare items, which were commonly used as high-denomination currency. Arena Net shut them down, but not before they were able to buy pretty much everything they wanted. The community is still trying to figure out how many ultrarare, limited-edition minipets were lost when the dupers' accounts were deleted. (The wave of bot-related account bannings in 2010 probably didn't help either, judging by the wails of some of the banned).
 * Most MMORPG service providers will conduct massive wipe-a-thons and server rollbacks when they confirm that a wave of duping has occurred. Items that were unique or virtually impossible to get before the dupes will naturally fall under this trope afterwards. Occasionally any in-game items that were used to trigger the duping will be removed outright rather than being fixed.
 * MMORPG Mabinogi has many of these associated with limited-time events. Not really important, since the vast majority of these items are purely cosmetic, none of them are Game Breakers or even particularly high-powered, and most of them don't last very long anyway.
 * Some of the main story quests have the option to skip them. Doing so loses a few good items or titles forever, or eliminates the ability to convert from Paladin to Dark Knight. It also makes some of the later story quests more difficult; though they're still available.
 * Special titles are available to players who "break the seal" on newly-released zones and dungeons by matching a particular set of conditions. Since each seal can only be broken once per server, they are unique, and unavailable to other players once the seal is broken. If the player character is deleted (by the player, or by the Game Masters for rules violations), the seal remains broken, and the title is lost forever.
 * Speaking of Nexon (at least in North America) Dungeon Fighter Online has special titles that grant players with all kinds of nifty abilities and stat bonuses. The title of Trailblazer was given to players who participated in the closed beta and is in no way obtainable at present time, making it royalty amongst all other entries in this trope. Lost Forever, indeed.
 * The Neopets Advent Calendar. Oh boy. If you miss out on a day's worth of free items, who knows what you can do...
 * You can buy them from another user's shop, most Advent Calender items are valueless until the next year because so many people have them.
 * A real example of this trope on that site is the fact that apparently there are a few very old retired items that no longer exist in the game at all because every copy was ate/discarded/destroyed by a random event/ or left on an account that was frozen or deleted due to inactivity, the fact that there are items like this was proven in an editorial, but they refused to say which ones...
 * In RuneScape, certain emotes and items can only be unlocked during special events. Emotes and songs can be unlocked when the event occurs next year. The items, however, are gone for good.
 * Also, some items like the Half Jug of Wine, Santa Hats, or Party Hats can no longer be obtained, and unlike the above items, are tradeable. This has made them extremely valuable as only a few exist. If a player were to drop one and no one picks it up, then it would be lost forever and that item would grow even more rare.
 * How valuable, you ask? Party Hats (colorful paper crowns that were a holiday drop during Runescape's very first Christmas), go for around 700 million gold!

Platform Game

 * Metroid: Other M keeps this trope running in the Metroid franchise. At one point in Sector 2, there is an area with a Missile Tank, which is behind a pillar. Unless you have a guide, chances are you'll miss it. Wouldn't be so bad except that the area suddenly succumbs to an avalanche after you solve the puzzle. This avalanche covers the entire area and you can never go back and get the items you missed, even after you beat the game.
 * Metroid Fusion has a couple of upgrades that become inaccessible after you get the Screw Attack. Most of them are in the section where you get the Morph Ball, which is sealed off during the fight with . There's a total of four power ups here that you can't get to.
 * In Mega Man X 6, Zero is Lost Forever (well... until X7, anyways) if X doesn't fight Nightmare Zero before exposing Gate.
 * In the various stages, there are Reploids for you to save. If a Nightmare Virus gets to them first, they're Lost Forever... and some of them give you useful things.
 * X7 also has rescuable reploids, problem is they're apparently made of paper, They die from the smallest amount of enemy contact, Sad part is you need 64 of the 128 reploids to unlock X. Its especially frustrating because your characters have a tendency to fall over when shot in Mid-air (Where most of these reploids are in some stages) and they just sit there, slowly getting up. When they do get up chances are the reploid you wanted to save is dead.
 * In Mega Man Zero 2, you collect Forms by performing certain tasks during missions. However, the game only gives you one Form per mission, and there are a limited number of missions, so it's possible to miss some Forms. Fortunately, there are more missions than Forms, and the New Game+ lets you try again to collect anything you missed.
 * In Mega Man Zero 2 and 3, collecting EX Skills requires maintaining an "A" rank or higher on almost every mission. Each EX Skill is specific to a boss, so you get precisely one chance to get each one per playthrough. And using Cyber-Elves gets points deducted from your score on every mission afterwards, even into a New Game+, so using too many Cyber-Elves makes A-ranking impossible and thus renders all unobtained EX Skills truly Lost Forever. True, there are Cyber-Elves that got you a temporary A-rank, but there aren't enough of those to get you every EX Skill.
 * Mega Man Zero 3 had a a special feature where you could activate Ciel's supercomputer and link up to another Gameboy Advance with a Mega Man Battle Network 4: Red Sun or Blue Moon cartridge and initiate a very special, one-time-only trade to get the exclusive Z-Saber chip. Unfortunately, it won't work for multiple games- just one. And guess what? The chip's not available on Higsby's ordering service! Buy another game copy, mooch off a friend's game, or dust off the Gameshark!
 * In Mega Man Zero 4, you could make items out of parts obtained from defeated enemies. Some items require parts from Moloids, an enemy that only appears during one mission that can't be repeated. If you didn't stock up on their parts during that one mission, you'll just have to wait until the New Game+.
 * Also, in the original Mega Man Zero, entire missions are lost forever if you get a game over and choose to continue instead of restart. And did we mention the game has barely any 1-Ups?
 * The original game also has the abandoned laboratory that serves as the introduction stage, which has a few Cyber-Elves and nice opportunities to grind crystals. An early mission that sends you back there ends with the lab self-destructing. You'll be forced to wait for the New Game+ afterwards.
 * The first game also has mission-specific Cyber-Elves that only appear if you defeat certain enemies during a mission. Fortunately, New Game+ remedies that problem, and by the second game, the developers made getting the Elves a built-in feature of any area, regardless of missing them on the first go-around.
 * Lastly, the first game has a door to Ciel's room that will only open if your rank is A or S. Inside is a Cyber-Elf. Screwed up the ranking to the point of no return- well, then- that Elf's LOST FOREVER!!
 * A glitch in the first few copies of Spyro the Dragon: Year of the Dragon makes the second egg for the first world's speedway level Lost Forever if you leave the level the first time you visit it without winning the event for it; afterwards, even if you do win the event, you won't get credited with the egg.
 * By definition, any game with a Point of No Return is going to have some items end up being Lost Forever, but Psychonauts is especially irritating. Once you, you can't return to the camp or Cruller's lab. You can still collect anything left in the mental worlds and redeem stuff in the final level, but if you missed any Psi-Cards, Scavenger Hunt items, or other collectibles found in the real world, too bad! You're prevented from getting to Rank 100 and getting the secret ending movie.
 * You are however warned explicitly when you reach the point of no return and given the option to turn back.
 * You also face this problem in Basic Braining. If you don't complete all six rounds of the punch game the first time you meet the level the game will disappear and you'll never get that PSI Cadet Rank, which makes it impossible to make the 100% Completion.
 * 100% yes, but Level 100 no. It's worth pointing out that the game's bonus level is actually the secret 101st level. There's no reward for getting to level 101, as opposed to 100, so the only real payoff beyond completionism is an early start.
 * Actually, there is a Steam achievement for reaching level 101. There's also an achievement for several other things that can be missed. For example, immediately after completing Sasha's Shooting Gallery, you can go to the parking lot and look in the corners for Maloof, to have a conversation that results in an achievement. Or you could do what the story tells you to do, which is go back to the Brain Tumbler, not leaving Sasha's room. This is one of many conversations that can be had after receiving each badge, but require you to track down everyone else.
 * One of the secret items in Braid cannot be acquired once you clear a particular world, forcing you to restart and solve every puzzle again in order to see the Best Ending.
 * Fridge Brilliance, actually. It was intended that players would miss the item on the first playthrough. Once they found out, only restarting the game would let them get it. The developers make the Player use the game's time rewinding mechanic in real life.
 * More Fridge Brilliance: the game's theme is about obsession and the dangers therein (maybe). The only way to recover that secret item? Start a completely new game to satisfy your obsession with One Hundred Percent Completion. Not only that, but the reward for One Hundred Percent Completion is the (probably).
 * Even MORE Fridge Brilliance: One of the levels in the world is named "irreversable".
 * You get the "Best" Ending on your first playthrough and the Bad Ending on the second playthrough. It's all Backwards.
 * In Banjo-Kazooie, there is a Mumbo Token in a waterlogged pyramid in Gobi's Valley, on the surface of the water. Collecting the Jiggy in the pyramid will drain the water, so if you don't get the Mumbo Token before you drain the water, it is Lost Forever and there will be no other way to get it.
 * Another one in Banjo-Kazooie is often missed by fans. There is a grille connecting the chambers with the picture puzzles for Mad Monster Mansion and Rusty Bucket Bay, but many fans do not notice this link. After raising the water level once, it is possible to go to the chamber with the Mad Monster Mansion puzzle and break it, then go through to the Rusty Bucket Bay puzzle, but most fans don't realize this and raise the water level twice, making the grille Lost Forever. Some of them have spotted the grille in the chamber with the Rusty Bucket Bay puzzle, but mistake it for a dead end. If discovering this upsets you, the Rare Witch Project wiki has a list of cheat codes that can be entered on the sandcastle floor in Treasure Trove Cove to open parts of Grunty's Lair, and among the more useless codes to open various grates is CHEAT THE GRILLE GOES BOOM TO THE SHIP PICTURE ROOM to open the grille in question (although entering more than two codes will prompt Grunty to erase the game file, and in the XBLA version you will lose your leaderboard status).
 * The XBLA version changed the note collecting so notes stayed collected as opposed to reappearing. This causes problems later in the game if a player chooses to do the Bottle Bonus Puzzles early in the game. In the puzzles the game simulates Banjo doing stuff; in two of the puzzles, this includes collecting notes, which, due to their non-reappearance, makes the notes disappear for good. The game is known for people overlooking notes and spending ages trying to find them; this only causes frustration. People spend hours trying to find the missing notes. Worse still, completing all the bottle puzzles gives an achievement which encourages people to do it.
 * In Banjo-Tooie, when speaking to Goggles for the first time, she'll give you the Amaze-O-Gaze Glasses (and thus the ability to zoom in and out during a first-person view). That is, provided that you haven't won the Tower of Tragedy quiz yet, otherwise you'll be permanently locked out of Bottles' House and thus will never get another chance to get the Amaze-O-Gaze. Not that you'd need it, anyway, since it's entirely optional.
 * The Jolly's Jukebox song "Sad Jinjo Houses" can only be unlocked by walking into a Jinjo house before the family is reunited. However, if you have saved all the Jinjos, the track is Lost Forever. Strangely, the tracks "In The Hall of the Zombie King" (heard in the Zombified Throne Room) and "Party at Bottles'" (heard by approaching Bottles' house after beating Tower of Tragedy but before beating the final boss) can be unlocked in the jukebox without even having to hear them.
 * In Prince of Persia: Warrior Within there are nine secret life upgrades. You must find all to get the Water Sword, which enables you to fight the Dahaka and get the alternate canon ending. Fortunately, the game allows for plenty of backtracking from the Central Hall, so most of the upgrades can be picked just before the True Final Boss. However, two of them are located in a One-Time Dungeon. Miss either and kiss the good ending goodbye.
 * All Sands ot Time trilogy games contain missable life upgrades; however, you're only penalized with a different kind of ending in Warrior Within for missing any. The upgrades have no bearing on the plot of the preceding Sands of time, nor in the third instalment, The Two Thrones. This last game also packs missable Sand Credits. Miss enough and you won't be able to pay for all the unlockable artwork. Not a big deal, unless you're after 100% Completion.
 * In Iji, if you miss one ribbon, the following ones will disappear. But the sector 7 ribbon fits the trope more: After the ship, there is a teleporter accessible by using the Nuke weapon's recoil. It's actually a shortcut, and using it causes the sector's ribbon to be Lost Forever.
 * Due to Real Life getting in the way, World e in the GBA Super Mario Bros 3, IN AMERICA! Due to the e-Reader being discontinued before the release of all the cards, only 10 of the World-e levels can be accessed, and only then if you can find the appropriate cards (tough enough as it is). The Super Mario Wiki has details.
 * The Tomb Raider series, of course, has countless missable secrets. Taking the wrong path in a level will bypass certain secrets, and you can't go back for them. In the Lud's Gate level, you must kill a guard without being seen to access an underwater room, if he sees you, it closes up for good. In the High Security Compound, there are two switches that each open a secret room much earlier in the level. If you hit both switches, it closes again, forever. Guide Dang It...
 * Jak 2 has a few one-time-only Precursor Orbs, most notably in the Strip Mine and Construction Site.
 * Actually, only the seven orbs in the Metal Head Nest are lost forever if you miss them. All other locations can still be reached after beating the game. Some are just trickier to reach than others, which is probably why some people think they're lost forever if they miss them (the Strip Mine, for example, can still be accessed via the warp portal in the prison cells where you rescue Jak's friends at the beginning of the third act).
 * In New Super Mario Bros. Wii, you get save file stars for accomplishing certain tasks. If you never make the Super Guide box appear, the stars will sparkle. However, if the Super Guide box appears on any level, even if you don't use it, you can never make the stars sparkle on that save file. This is also a rare example of a retroactive Lost Forever, because you can lose the sparkling stars, even if you already have them, if you trigger the box.
 * Super Mario 3D Land does something similar. Die five times in the same level, and you get a special powerup that makes you invincible. But then, even if you don't use it, the save file stars don't sparkle.
 * Super Star Wars: The Empire Strikes Back has Force power ups for Luke to collect as part of his training with the Force. Most are in plain slight but others are somewhat hidden in the level. If the player beats the level boss and misses on a few Force powers, they are gone for good the player can be at a handicap later when they use Luke later on. The sequel adverts this by giving Luke all of his powers in the start and doesn't need to find them again.
 * In Space Station Silicon Valley there is a trophy on one of the levels that you cannot pick up (you will only walk through it), and as such the bonus level is only accessible through cheats.

Puzzle Game

 * In Puzzle Quest: Challenge Of The Warlords, every enemy (and learnable spell) can be attained at leisure... except for the Imp spells (Burn, Taunt, and Zap). The Imps only appear on one spot of the map, which only unlocks after you've completed "The Marriage" subquest in Enmouth, and will disappear the moment you return to report to the Queen. You have to stay there and defeat three Imps in a row before capturing one, and the aforementioned spells turn them into Demonic Spiders if you're playing as a Fighter or Wizard.
 * World of Goo has this in a much smaller degree in the form of a Bragging Rights Reward known as an "OCD". There's a glitch in the game preventing the gamer from getting the OCD Achievement in the level "MOM's Computer" after completing that level once.

Real Time Strategy

 * In Medieval 2, generals can sometimes gain Ancillaries, technically characters following them around but essentially a stat boost. Most of them are gained through specific but generic actions like winning battles or being in a town/castle when a given building is completed. However, some of the most powerful ancillaries are historical ones like William Wallace or Machiavelli, and those can only be gained in very specific circumstances, not known to the player unless he has peered through the game files. Joan of Arc, for example, can only be gained during a 20ish year span (1 turn being 6 months in the game), only for French players, only if France and England are at war late in the game (which is unlikely, since both countries are in each other's way, and one usually destroys the other in the early game) and only if the given general wins a battle against the English in which the odds were against him, but not too much.
 * Salvaging in Homeworld is tremendously powerful because it allows you to exceed the arbitrary build limits for your fleet. For example, you can build only four heavy cruisers, so any that you fail to capture in the missions they appear are Lost Forever. Due to Cosmetically Different Sides, heavy cruisers are arguably not a true example because you only miss out on extras. A purer example occurs with the Gardens of Kadesh missions, where the enemy units are unique. Multi-Beam Frigates pack a meaner punch and a much cooler attack than your ion beam frigates. You can nab at least 18 of them, which in a wall formation will make short work of any ship.
 * The first Pikmin game had Libra, a piece of the Dolphin found in the Forest Navel that hangs on a high platform separated from the rest of a map on a cliff. Although it is possible to get Libra down off the very top of the cliff without problem, the cliff is narrow and there's very little room to meneuver, which makes it possible that your pikmin will miss-step coming down, falling down the bottomless pit around them and taking Libra down with the troop. Once lost, it is lost for good and won't respawn unless you restart the game, and because Libra is one of the Dolphin's 25 vital parts, you shot down any chance of winning the game if you lose it.
 * Quite a few in either Tomba game, but the most unpleasant is in the sequel. To complete "Hide and Seek", you have to get a girl out of a hole in a wall. To do this, you throw a snowball into the hole under her, which slingshots it into her and knocks her to you. Capture the Ice Evil Pig before you do this? The snow melts... and you can never get her out. Doing this prevents you from doing "Who's the Liar?", which prevents you from entering one of the Secret Towers, which keeps you from getting one of the best weapons in the game. A hat-trick of Lost Forevers from one misstep!

Rhythm Game

 * DJMAX Technika's Weekly courses. Each one is available for one week, then is gone permanently, replaced by the next Weekly course.
 * And for that matter, Technika's Platinum Crew Service. In mid-July 2010, the Korean servers for Platinum Crew went offline, forcing arcades to upgrade to DJMAX Techinka 2 if their customers wish to continue playing online content.
 * Rock Band:
 * Challenge rewards can only be obtained one time per band. While the "impossible [instrument] challenges" clearly show what the costumes look like (before coloring), the "Impossible Marathon, part 2" challenge has a reward of ONE (not a set. ONE) "crazy instrument" for each active player, corresponding to whatever instrument that player cleared Painkiller with. In order to get all 4 crazy instruments on one character, the entire challenge ladder must be gone through four times, each one in a different band. The amount of time one such run takes is comparable to the time it takes to clear Endless Setlist II.
 * Remedied in Rock Band 3 - unlock once, use on every character you want for that profile.there are a couple of songs
 * There are a couple of songs that were pulled from the store due to copyright issues.

Roguelike

 * In Roguelikes (Angband, for example), items are usually unidentified when you first find them, and they can always be generated again later. This includes unique "artifact" items, but only if you don't identify them, since artifacts are only generated once per game. If you ID an item and it turns out to be an artifact, it is Lost Forever when you leave the level and you're not carrying it.
 * TOME has a few dungeons with special named levels, which are different in that they aren't randomly generated, and thus the same in every game. They also have the same unique monsters and artifacts in every game. They also disappear if you leave (for example via the down staircase) and if you attempt to go back to it, you'll just get a randomly generated level instead. So, you only get one shot at grabbing those artifacts (whether found on the floor or dropped from a unique) before leaving the level, or they're Lost Forever. Make sure to have some free inventory space when you get there.
 * In ADOM, the Pyramid (which holds two awesome artifacts) is a prime example of this trope. It closes as soon as you reach level 17. Besides, it is a rather difficult place, which means that you want all the skill you can. So...

Role-Playing Game

 * In Final Fantasy II, you can permanently miss the Blood Sword, a gimmick weapon that works wonders on the final boss. It's in Paul's stash, which he'll share with you if you ask him about the key term "Cyclone." But you can only learn that term from Hilda, and you must do it after the cyclone appears and before you call the wyvern so you can enter it.
 * The above only applies to later versions, as the original and the PSX version had a second Blood Sword in the Fynn Dungeon.
 * In the PSP version, there's an Amano art gallery you can unlock as you play through that requires, among other things, 100% bestiary completion. Unfortunately for you, partway through the game all encounters on the overworld become harder--with absolutely no warning beforehand, incidentally—meaning that if you failed to hunt down and kill those monsters before breaking the seal on Ultima...well, sucks to be you.
 * Similarly, if you want more than one character to learn Osmose, you're going to have to grind either the Coliseum, Fynn Castle, the Cyclone, or Castle Palamecia while they're available—those are the only places to find Wizards, a rare (and in early areas, horrifyingly fast and powerful) random encounter that will even more rarely drop the tome needed to learn Osmose, and once you complete them, you can't go back. As wise use of Osmose can make characters effectively immortal, you have good incentive to do this. Have fun grinding!
 * Final Fantasy IV is generally in love with this trope. 90% of the cast will enter the party for just a single dungeon, and then leave forever based upon the random swings of the plot. Unless you've played the game before, you'll never guess when your little mages that are holding an ultra-rare staff are just going to run off without a moment's notice. There are a few areas where the game is twice as hard as it should be only because you're stuck with a weak party because your entire A-team was taken away by a shipwreck. Or where you're just stuck with pathetic semi-useless characters (Tellah, Edward). The DS remake expands this to the one-use skill teaching items called Augments, and combines it with a little Guide Dang It. If you give Augments to non-permanent characters, you're never going to be able to use that skill again. Also, if you don't give the exact number of Augments to the right people before the plot takes them away, you can never get some other skills. Example: If you didn't give three Augments to Porom and Palom before they leave, you're never going to get Doublecast. This is doubly cruel for those who have played the game before, since it just goes against common sense to give skills to characters that aren't going to be around in the end game.
 * Of course, considering that there are some Augments that aren't all that good and are re-obtainable throughout the story, this just becomes a slightly tedious exercise.
 * Final Fantasy V has quite a number of these, . Although some spells can be bought at the Phantom Village, summons like Shiva are just some of the things that can be Lost Forever.
 * In Final Fantasy VI, the Atma Weapon sword can be found in the cave leading to the Sealed Gate. This cave is gone forever when the entire continent suddenly takes to the air.
 * The GBA version gives you a second chance to get this item.
 * One of the characters in your party, the moogle Mog, can dance to change the terrain and cause various other effects in battle. At one point in the game (in the World of Balance section, before ), you have the choice to save Mog from falling off a cliff, causing him to join your party at that time, or getting an accessory that will halve the MP cost of spells. If you choose not to get Mog at that time, you can still get him to join again later in the game. However, one of his dances, the Water Rondo, can only be obtained when he's fighting in water. Since there is no area where you fight in water in the World of Ruin, if you choose to get the accessory, Mog's Water Rondo will be Lost Forever.
 * The Game Boy Advance remake adds a fight against Leviathan in the World of Ruin, which takes place on a watery background, giving you one more chance to get the Water Harmony (as it's re-named), but after defeating Leviathan, the dance is, again, Lost Forever.
 * If you don't wait for Shadow on the Floating Continent, you lose him permanently as a party member.
 * You can permanently miss out on the Ifrit Magicite... but that would require you to deliberately ignore the thing and move on without it.
 * Some of Strago's Lores can only be obtained from bosses giving you only one opportunity to learn it.
 * However, Strago's ultimate Lore is an exception—even though the boss who has it is supposedly unique, when you come back it will respawn so you can fight it again if he didn't learn its ultimate attack.
 * The Bahamut Esper can be missed entirely if you manage to use X-Zone on the boss Doomgaze. This can be achieved by using the Vanish spell on him first. The other "Instant death" combo, Vanish and Doom will work, but using X-Zone removes Bahamut from the game.
 * Actually, its not permanently missable in the original game. Vanish + X-zone just, for some really weird programming quirk, does the opposite and fully heals him, letting you still have a chance to refight him. Many just assume he's dead and figure they missed it for logical reasons. The GBA version, however, has it permenantly missable provided you have not defeated him on the Overworld but defeat him for the first time in the Soul Shrine.
 * In Final Fantasy VII, the Wutai Sidequest must be started before disc three, as it suddenly becomes inaccessible after disc two due to a sudden plot development. Many types of materia, including Ifrit, Ramuh, W-Item, Phoenix, and Neo Bahamut, are one-shots (it might be possible to dig up some or all of these materia at Bone Village). You only have one chance to acquire Barret's ultimate weapon, and it doesn't appear unless he is in your party at the time. All items located at Shinra Headquaters, including Cait Sith's ultimate weapon, are missable because you only get to visit there twice. These are just a few examples, in fact the game is so rife with Lost Forevers that there is a guide on GameFAQs with the sole purpose of listing them all.
 * Aeris's Level 4 Limit Break as well, to an extent. You can get it at any time, but after she dies, what's the point of it?
 * Ghost Hands, which drains MP from the enemy, are only obtainable before Shinra levels Sector 7.
 * Some of the enemy skills can be lost forever. Trine can be only be learned by two bosses and one enemy in a one visit location. Pandora's Box can only be learned from Dragon Zombie who can only cast once per save file due to a programming error.
 * Subverted in all the stuff in Midgar. It's lost...for a really really long time.
 * As far as i can tell Vincent's Level 4 Limit Break and ultimate weapon is unaccessable if you dont go to Lucrecia's cave early enough and enough times.
 * While the Gelnika can be visited any time, the Turks are unavailable during disc three so the fight with them can potentially be missed. And speaking of the Turks, all of them carry unique pieces of equipment that must be stolen during the fights against them on disc two. Furthermore, if the player completed Wutai, they have the option of skipping the final showdown with them at Midgar, thus losing the aforementioned equipment.
 * Many of the Guardian Forces in Final Fantasy VIII can only be drawn from bosses and secret bosses, which are by definition a one-shot deal. You get a second shot at many of these with a different batch of bosses, except in the Japanese version, for some reason.
 * In addition, upon arrival to the 4th disc, all of the towns in the game are locked off, which also seals off quite a few sidequests and, by extension, unique rewards.
 * The rare cards you can win by playing the in-game cardgame can also fall victim to this, since the rare cards are only held by one person, and you might very well lose the chance to speak to these people later.
 * Actually that isn't necessarily true. Whilst it's possible that Ellone is one of the cases where it can happen there is nevertheless hope for players that might have missed it. As long as the player completes the Card Quest then all of the Group Members will be available on the Ragnarok during Disc 4. One of the players actually plays virtually all the rare cards in the game meaning if the player missed out on any then it could be gotten there. The only card that is extremely rare and really fits this trope is the Pu Pu card.
 * Final Fantasy IX has the Excalibur 2, Steiner's Infinity+1 Sword, which is only attainable in the game's final dungeon...and vanishes if it takes more than twelve hours, from the start of the game, to get there. Perhaps less obnoxious than most examples of the trope in that it is meant to be an award for speed running through the game, rather than an arbitrarily unobtainable item.
 * This game has more Lost Forever stuff than most of the rest of Final Fantasy combined, and that's saying something. Anyone who wants to get all of the little flavor awards has to completely re-explore each city at every plot point, including so many Guide Dang It moments that the official guide doesn't cover them all, instead referring to a website accompaniment that no longer exists.
 * Japanese players didn't even get the luxury of having a strategy guide at game launch to find all of said crap, due to Square's marketing approach ('hardcore' gamers who would find and reveal the secrets through word of mouth wouldn't need a jump start, apparently.)
 * One particular big Lost Forever in Final Fantasy IX example is the end of Disc 3/start of Disc 4, where a good deal of the towns, such as Conde Petie, on the map become unaccessible because of the plot.
 * Disc 3-4 transition closes up Esto Gaza, the only place you get Scissor Fangs. The other one is synthetized with a one-shot (but thankfully unmissable) weapon, the Dragon's Claws, and the Tiger Claws, which can only be bought on Daguerreo, during the events of disc three. If you get to disc four without either Scissor Fangs or Tiger Claws, bye-bye Aura flair.
 * Scissor Fangs be damned, Esto Gaza is also the only place in the game that sells the Octagon Rod, which is the only item that teaches Vivi all 3 of his -aga spells, making him a lot less useful if you miss it since without them, he has no way to hit multple enemies late in the game without either wasting a ton of MP to do it, having a chance to miss enemies entirely or damaging the party members that don't have armor that absord Shadow-elemental attacks in the process.
 * Perhaps because IX was so hellish, Final Fantasy X averts this almost entirely. The game mostly goes out of its way to avoid this trope, allowing virtually every item to be available in infinite supply by killing, stealing, or bribing from enemies, mainly from those found in the Bonus Dungeon and Monster Arena. The only exceptions are a few Al Bhed primers, which translate bonus dialogue. And, no, despite what you may have been told, it's impossible to miss out on the summon Anima.
 * Of course if you're playing the International/PAL version after a certain point in the game certain areas can become blocked off by the insanely difficult if not nigh impossible (for the average player) dark aeons.
 * A pair of oddball items that are a result of a programming mistake are missable; namely, the weapon with No Encounters (dropped by Geosgaeno) and the shield with Magic Counter (sold by the hovercraft on your first visit to the Calm Lands). However, these aren't exactly crucial to the game and merely serve as collector's items.
 * A better example of this trope is the Master Sphere item. In the NA and original versions, you're limited to 10 (which can't be missed). In the International release, they are rare drops from the dark aeons and Penance (and his arms). This lets you get 99 (by killing Penance's arms and then running away), but once you kill Penance for good, this opportunity is gone.
 * Final Fantasy X-2 ups the ante and features numerous examples of one-time Guide Dang It Lost Forevers - especially completion percentage points, which can be Lost Forever if you ever use the scene skip feature during a plot scene. All the more frustrating, they are required in order to achieve 100% completion, which has a reward beyond bragging rights.
 * Final Fantasy XII has the Zodiac Spear, which, unless you avoid opening four arbitrary chests earlier in the game, can only be acquired from a chest that's only there 10% of the time and only has the dang spear 1% of the time. (That's nearly 700 reloads, on average.) Also, some items, such as Slime Oil, are only available en mass from spam-stealing from a certain gone-after-you-defeat-it-once enemy (Though you can obtain the only one that is actually required by completing 90 tiers of racing, much later in the game).
 * The chest holding the Demonsbane sword, obtained from the Tomb of Raithwall, will only appear if you defeat the first Demon Wall, --the one you're supposed to run away from, since its stats and abilities are far beyond what normal progression would allow your party. Even if you do defeat it, prepare to run back and forth from the entrance to the chamber where the chest appears, as there's a random chance of the chest containing Knots of Rust instead... and that's if the chest even appears at all.
 * It is possible to miss the Omega Badge and therefore screw yourself out of the Wyrmhero Blade. Granted, you pretty much have to be doing it on purpose, because no gamer in his/her right mind wouldn't pick up loot dropped by a Bonus Boss.
 * In MARDEK RPG, once you enter Moric's battle-saucer in chapter 2, you've permanently sealed off the catacombs, lost your chance to unlock Cambria, and boosted the hire price of Zach by 1000%. Also, when you go into the throne room in chapter 3, EVERYTHING is closed off until the chapter 4 release, and some stuff will probably remain lost even then.
 * In Kingdom Hearts, finding and using multicolored marks called Trinities was one of the requirements for 100% Completion. In Halloween Town, a Red Trinity can be found in the base of Oogie's Manor, and you must use that Trinity before fighting Oogie Boogie for the first time. After you beat Oogie, he merges with his manor, and beating him makes him collapse to the ground, thus rendering the Trinity Lost Forever. Another catch is that to use the Trinities, you have to have Donald and Goofy in your party for them to work. Many players who couldn't be bothered to switch Jack Skellington out of their party at the Save Point at the top of the manor and backtrack to the Trinity with Donald and Goofy ended up tearing their hair out in frustration.
 * The Final Mix version moved the location of that trinity, preventing it from being lost forever. However, it introduces a different problem...
 * At least the game still has the treasure in a little ...um... thing where Oogie's manor used to be.
 * Kingdom Hearts 2 had a few harmless missables during the tutorial, but considering it was made by Square Enix (see the opening entries in this trope) it's surprising that otherwise, the series has avoided this problem since then. But Birth By Sleep, which requires 100% to get the bonus ending, can lock you out of a few otherwise boring chests during the final chapter. If you miss them, you'll have to And you just know it was for a Potion or something...
 * Remarkably, Lufia II: Rise of the Sinistrals averts a situation like this by including a shop late in the game where you can buy back any item you've ever sold. An interesting example of realism in an RPG...well, if you ignore the improbability of all of your items being resold to the same shop.
 * Less unrealistic than it sounds: the entire town in question has a rather unhealthy fixation on the heroes, and it's implied they go out of the way to find everything you've so much as breathed on and sell it as a collectors item. The entire thing is very creepy.
 * While very hard, it's possible to make any and all digimon become Lost Forever in Digimon World 3 or the PAL release Digimon World 2003. Digimon have a "requirement" to be met before you can actually recruit them, the requirement is always a minimum and maximum level. In short, if ALL of your current digimon are above that level you just can't get that other digimon.
 * The easiest to lose like this is Veemon, the only digimon which you cannot get in any of the starter packs and also arguably the best rookie in the game. The max level for recruiting him is freaking 30. And you only get Mega-Level Digimon on level 40. Fortunately, the fight for recruiting him is fairly easy.
 * In Dragon Quest VI, you can lose a character if you tell him the wrong thing at the wrong time. To be specific, if you tell the truth   before giving him the, he'll leave the town never to return. To be fair, at least in the DS version, a lot of the NPCs in the town tell you that doing so is a bad idea since they hail him as the town's saviour and  , and the game itself gives you multiple prompts on whether you want to do it.
 * Dragon Quest VII for the Playstation does not allow you to collect certain NPC's for your island after the first or second disk, which means a certain amount of Tinymedals will always be out of your grasp.
 * Hell, you can lose an entire town! If you don't resolve one of the towns' problems properly (which takes 3 times), the town's still ruined in the present.
 * In Dragon Quest VIII, the items in the town of Neos are Lost Forever after a certain major plot event occurs. The game also doesn't prevent you from selling items with finite availability. Shopkeepers are nice enough to warn you when something you're about to sell is one-of-a-kind, but they usually fail to warn you against selling items that are relatively common, but have limited availability (Rare Drops, Casino wins). Such items are often required to craft the best weapons in the game. Of course, there's seldom if ever any indication of this in-game. Therefore, most knowledgeable players follow this mantra: don't sell anything that can be used in the Pot, since it'll show you which items you can and can't use in Alchemy.
 * Eternal Sonata has an old lady that can be spoken to in Chapter 4. Doing so will allow you to access a Score Piece later on. However, if you don't speak to her in Chapter 4, she will be sleeping for the rest of the game, making that particular Score Piece Lost Forever.
 * In the main series of Pokémon games, you have only one chance at capturing certain incredibly rare Legendary Pokémon (although you can trade for them with other cartridges). Of course, the fact that you usually challenge these Pokémon to battles, and can fight them at any time in the games, makes it unlikely that anyone actually will miss them, because most players just save before the fight and reload until they capture them.
 * In Pokémon Diamond & Pearl and Pokémon Platinum, there is a hidden HP Up at Lake Valor that can only be got while the lake is dried up by the Galactic Bomb. . If you return to Lake Valor when the lake is filled with water again, you can't get it.
 * Another kind of Lost Forever is the event-only Pokémon, such as Mew. Usually there will only be one event per generation of the game to get these in a particular area of the world. If you miss it, you have to either trade with someone who managed to get one to add it to your Pokédex, or else cheat for it. (There is a glitch in the original games that allows you to fight a wild Mew, but it requires you to have not fought a certain type of trainer.)
 * This Lost Forever is why it's considered completely acceptable to use cheating devices in order to obtain certain Pokémon.
 * Pokémon has occasionally done this with other things. In the Gen. I Red/Blue versions (and the FireRed/LeafGreen remakes), once you speak to the captain of the S.S. Anne, it leaves port and never returns, so you can't fight any of the trainers there or obtain any of the items. In the original Gen. III games (Ruby/Sapphire), Team Magma/Aqua's base was permanently sealed off after a certain point, so if you didn't already get the Master Ball, it was Lost Forever. (Emerald changed this.)
 * Averted in Pokémon XD, where if you knock out the Shadow Pokémon during a battle that is not repeatable, you will have another chance to capture it. A trainer named Miror B. will have all the Pokémon that you lost the first time. You even get a radar to tell you when he is around to battle. Although after you have all of the Shadow Pokémon, he destroys the radar.
 * Speaking of Miror B., a minor trainer (with a unique model and a sped up version of Miror B's battle music) appears in his place after you beat him, but disappears eventually. Seeing as how you would never go through a now empty dungeon, pretty much no one is going to see him without being told.
 * Also averted in Pokémon Colosseum (XD's predecessor), where you also have unlimited chances at getting each Shadow Pokémon - although some aren't easy to find (their trainers tend to be in a completely different place), they are all there.
 * Pokémon Platinum onwards averts this. In Platinum, Giratina can be re-encountered in Turnback Cave, and any other legendaries you accidentally KO will return if you go beat the Elite Four; the latter feature has been retained in all games since Platinum.
 * In Gold/Silver and their remakes, this also applies to Red after you defeat him. You can also re-battle all Gym Leaders in HeartGold/SoulSilver (with stronger teams) for up to several hours during a certain parts of the day during the week with no limit on how many times they can be rematched on their time off (such as Pryce preferring to battle on Monday mornings; if it's 4 AM or later but before 10 AM, he can be fought any amount of times within those hours) after you encountered them out of their arena (with the exception of Chuck; since he meditates under a waterfall 24/7 his wife gives players his number anytime on any day of the week).
 * With Darkrai, if you go into Canalave Inn, fight it during your sleep, and beat it without capturing it, you wake up. After leaving the building, you can go right back in and repeat until you catch Darkrai.
 * The same thing happens with Arceus and the Azure Flute: if you knock it out, the entrance to its domain can continue to be opened and you can keep re-encountering it.
 * The same goes with Victini in Pokémon Black and White; you can beat him as many times as you like, but he'll keep coming back until you catch him.
 * This was particularly bad in Crystal version, where knocking out one of the Legendary Beasts not only prevented you from claiming that one, but also from accessing Ho-Oh.
 * It'd be really nice if you had the option to replay plot scenes you've passed in Pokémon Mystery Dungeon, but alas...
 * In another sense of the trope, if you're raising a certain Pokémon, it can lose certain attacks forever if you evolve it too early (or too late in the games without the Move Tutor).
 * Get the event Celebi in HG/SS? Better make sure you play the Giovanni sidequest before you transfer your 'mon over to Black and White.
 * Dark Cloud 2 has you taking pictures of various enemies and items, many of which are Lost Forever, including one-shot bosses.
 * In addition, a glitch in Chapter 3 can cause chests that contain Fruits of Eden, a valuable item that increases your characters' maximum HP, to be Lost Forever. One set of chests will disappear if you fail to open them immediately after they appear; if you open another (specific) chest before a later chapter, a chest that should appear in that later chapter will never appear at all. Thankfully, the rest of the chests in the game appear to be free of glitches.
 * The, the Chapter 7 dungeon, goes away at the end of said chapter, taking its Medals and Invention Ideas with it if the player doesn't complete it by that deadline. You also lose.
 * A way to get around the Lost Forever photographs without sacrificing progress is to keep a second save file not too far past your current one: if you realize too late that you've saved over a Lost Forever and are reluctant to repeat a difficult boss or level, you can use the other file to snap that shot, save it to the Album, and retrieve the same photograph using the latest save file. The only thing lost will be the Photography Score points.
 * Tales of Symphonia has quite a few treasure chests that can only be accessed once. As there is a reward for getting them all, this is extremely frustrating. However, this game is basically designed to be played more than once, using the New Game+ feature to carry over your rewards from previous playthroughs; it's literally impossible to get everything in the game in one run, even if you know how.
 * That's not all in Tales of Symphonia. Several sidequests become lost later in the game... That is, until you see the very last cutscene before the final boss, in which not only will the lost sidequests re-open, but at least two new sidequests will open. Thanks a lot for freaking me out with Yuan's ring, ToS...
 * Those looking to achieve One Hundred Percent Completion also need to use a Magic Lens once on each and every type of enemy in the game to complete the Monster List and get a reward. This includes bosses, whose Monster List entries are Lost Forever if you don't use a Magic Lens on them before you beat them. However, the Monster List can be carried over to a new playthrough in the New Game+ feature, allowing for another chance.
 * Worse then that, Raine has to be the one to scan them or you don't get the full entry. The exceptions are fights that she can't be in, such as various Duel Boss fights, and 2 unique enemies found before she joins the party, where everyone gets the full info.
 * You do not need to have Raine or anyone else scan the monsters to get credit for them in Symphonia. If you fight them, they go in your book, and it counts. The only difference is that not all the info will be in your book if you don't have Raine Magic Lens them. You can still "complete" the book and get the title even when it's full of question marks.
 * Another ToS sidequest this trope applies to is one involving a set of three optional bosses, the "Sword Dancers." If you haven't beat one by a certain point in the story it disappears forever. Also they have to be beaten in order - if you miss one the ones after it won't ever appear... which screws you out of the prize for beating all three - the Kusanagi Blades, Lloyd's Penultimate Weapon.
 * Another Tales (series) example, Tales of Vesperia is especially bad about this. Most sidequests (and the items, outfits and cities unlocked by completing them) have a very specific time frame in which you can complete them. Once that time's up, it's Lost Forever. And it doesn't help that there's usually absolutely no indication that a sidequest is even there. So, there are two strategies: Talk to everyone in the town you're in before moving on and hope you'll stumble across something, or just buy the strategy guide. It wouldn't be so bad if every single sidequest in the game was missable.
 * Along with this, an entire dungeon can be missed if you don't go to a certain random location before a key story event. At no other point can you go to this location and get the quest that opens the dungeon. What makes this especially bad is the fact that you have to go to this specific location, at a specific time, twice!
 * Don't forget the Secret Missions: bonuses awarded for carrying out certain (unhinted) actions during certain (unhinted) boss battles. You have to complete them all for one of Yuri's Titles.
 * Another fun example: the first two steps of a subquest that awards Judith's second-best weapon starts hours before you've even met her. Both steps involve immediately retracing your steps after you've been implictedly told to move forward, and must be done before entering Capua Nor.
 * In yet another Tales (series) example, Tales of the Abyss is prone to a great deal of Sequence Breaking that will render many skits, titles, costumes, items, weapons and sidequests utterly Lost Forever. Events need to be triggered during a very small window and chained with secondary and tertiary events that happen well into the game. Miss one step or take the wrong one and it's goodbye Infinity+1 Sword. This is particularly frustrating because 1) events are activated and deactivated seemingly at random, providing no heads-up whatsoever as to their importance, and 2) you're stuck for the most part in a linear quest that allows for very little roaming.
 * Skies of Arcadia averts this for every collectible... except treasure chests. And finding all of them is part of getting Vyse's Infinity Plus One Title.
 * The king of this trope, however, is likely the first Baten Kaitos game. As if getting 100% Completion wasn't hard enough (there are 1,000 distinct items to collect), many of the items are one-shots, and some can only be acquired by letting other items age, in real time, over days or weeks, and you have to take a picture of every single enemy in the game, including one-shot bosses.
 * Here's just one heinous example. To explain: in order to get 100% completion, you must take pictures of every character in your party. Every time you do so, there is a small chance that said character's photo will have a particular feature; this is called a rare shot, and naturally, you must also take rare shots of every character in your party. It so happens that in ONE particular boss battle, one character's appearance will notably change. Not only must you take a picture of that character in that state, but you must ALSO get the rare shot, and the only chance you have to get both of these pictures is in that one boss battle!
 * Diadem. Within a relatively short time frame, you have four bosses to photograph, six Auras obtained during a plot event through counter-intuitive means, each of which transforms 5 times over the course of the game and a merchant who sells a unique item and disappears after a plot event. Said merchant also blends in to the stylised background. Thats 41 items total.
 * And about those transforming items? After the game's first big Wham! Episode, the party gets scattered across the five continents. If the characters have transforming magnus (particularly the Auras) in their decks and you don't get them back before they change twice, you'll miss a transformation. Also, to get back four of the five missing party members, you have to fight four minibosses, one which must be faced with nobody but Xelha in your party. If she doesn't have a camera, then that boss' photo is lost. And if you left an Aura in the deck of the final party member, you'd better start speedrunning to get that character back (doesn't help that you have to go through two That One Boss fights, as well as two long dungeons to get there).
 * The Alfard Empire in general. The enemies you face there change every time the plot demands you go there, and then there's the Phantom Goldoba... Just to be on the safe side, visit the room in the front of the ship last. There are no items in there, and you have to visit every room before the boss appears, so make sure you get all the items before entering that room.
 * On your first trip to Mira, you have to go through a portal, keeping up with a character who will later become a party member while enemies try to assault you. You can shoot them down to keep from getting into battles with them, and shooting down an entire formation will net you a reward. If you miss a reward you want early, you can just intentionally fall too far behind to start over, but the reward for the very final group is Secret Recipe 4, which can't be obtained anywhere else. (The reward for group 10 of 13 is also essential, as it is Lyude's Level IV special move and by the time it appears as a random drop, it's probably no stronger than your regular attack magnus.) Just don't shoot down everything, because you won't run into those enemies again and you need to add their photographs to the list.
 * Perhaps because Eternal Wings was so horrible with this trope, Baten Kaitos Origins seemingly goes out of its way to avert it...though it isn't perfect. The "Tub-Time Greythorne" and "Warm Cheers" magnus (and by extension "Icy Jeers" which it ages into, and also by extension the sidequest that uses it) are missable after a certain plot event that occurs very late in the game. There are also four enemies that can be missed for your enemy list; one is the Ballet Dancer, the only random encounter in a one-time area that doesn't show up later in the Coliseum, but the really nasty ones are - the player is offered an option for whether to fight them. Saying "no" robs you of a perfect enemy list, saying "yes" robs you of the best ending. Thankfully, the player's magnus and enemy listings can be carried over to a New Game+, so even these things aren't strictly Lost Forever, and considering that there are only around 650 magnus to collect and about 130 enemies, it certainly did a better job than its predecessor.
 * Star Ocean the Second Story seems to have a large Lost Forever when the player loses access to ... but thorough investigation will reveal it is possible to return at the very end. Indeed, there is a Bonus Dungeon there.
 * Both Star Ocean 1 and Star Ocean: The Second Story do contain plenty of Lost Forevers, mostly in the form of optional characters. Both games only allow certain characters to join the party if other characters are not present - enforced either through specific scripted events, or through the party size limit of eight characters (opportunities to remove characters from the party are very limited). Additionally, Star Ocean has a specific point where you can permanently lose the chance to gain a specific party member by leaving the room - without any indication, before or after, that this has any significant side effects.
 * Another big one in Star Ocean: The Second Story is the Sharp Edge. It's a rather weak weapon for Claude that you can only get if you take second place in the fighting tournament, then speak to a specific NPC. Oh, wait, after the tournament was over, you left town BEFORE you spoke to that NPC? Guess what, the sword's Lost Forever. And did you know that Claude can customize it a few times and end up creating his Infinity+1 Sword? Guess you shouldn't have forgotten to get it!
 * Another interesting variance from Star Ocean: The Second Story. There is a particular hidden witch you may talk to in an early town, which promptly becomes uninhabitable a few minutes of game play later, and then much later in another town. If spoken to in both locations, she unlocks Indalacio Limiter Off, an alternate form of the last boss. It's a variance due to the fact that most players don't want this to happen, as he will destroy you.
 * The Elder Scrolls IV: Oblivion made great effort to keep any quest from being Lost Forever, through completing other quests—although this does cause some confusion, such as a thieves' guild quest where you steal from the Archmage. No big oddity there, until you realize that.
 * And while it's pretty good at not having quests Lost Forever, it's not good at all with items. Specifically, one of the guild merchants sells a bunch of rare items. He's the only person in the game you can get these items from. You have to kill him for a quest. He also sells a bunch of rare spells, but you can get those again once you're done with the quest line.
 * There's another guild merchant with a unique spell that only he sells. And he's killed as part of a quest. If you didn't buy the spell from him before he dies, it really is Lost Forever - no other spell in the game has that type of effect!
 * Another example in the Knights of Nine expansion, in order to receive master level training from a trainer requires a recommendation from an advanced level trainer. It just so happens that advanced trainers in restoration get killed during the Knights of Nine story line and their replacements do not give you the recommendation.
 * The main quest requires the player to sacrifice a Daedric artifact - those are one-of-a-kind items obtained through completing a quest. Once sacrificed for the quest, the artifact can never be recovered. To add insult to injury, most such artifacts are not very useful, of limited scope, or only good for entertainment value - but the main quest points the player towards the quest that gives Azura's Star, arguably the best Daedric artifact in the game...
 * Also, upon completion of the game,  To be fair, this makes perfect sense, but since the items you receive from in game drops and the enchantments you get from the Sigil Stones are based on player level, anyone who runs through the main quest quickly before doing any side quests will lose the best enchantments in the game.
 * The player can invoke this trope deliberately with the Dark Brotherhood initiation quest. If you murder someone ingame (whether deliberately or not), the next time you sleep you'll be visited by Lucien Lachance of the game's assassins guild. He'll give you a dagger called the Blade of Woe and instruct you to kill a man named Rufio to be welcomed to the Dark Brotherhood. You don't have to do it, but the dagger he gives you counts as a quest item - meaning it's stuck in your inventory - until the end of the Dark Brotherhood questline. If you have no intention of joining the Brotherhood, and you don't want to carry the Blade of Woe around indefinitely, you can kill Lucien as soon as he gives you the quest. On the plus side, you can now drop the Blade. On the negative side, you can NEVER join the Dark Brotherhood at any point in the game, making the guild and all its related quests lost forever.
 * Trope invoked in another offshoot Daedric prince quest where, in a realized case of having one's cake or eating it, Clavicus Vile offers to give you his amazing Masque of Clavicus Vile—headgear that increases social prowess (very) slightly—in exchange for the Umbra Sword, one of the game's (two?) optional Infinity Plus One Swords, which you must retrieve from a woman (named Umbra) whom is under the direct influence of the sword's former wielder... Umbra (a difficult fight, unless you're a powerful Mage). Incidentally, Clavicus Vile gives you an artifact (actually, it just sort of appears in your inventory), styled after his faithful, demonic companion, that advises you to abscond with the sword, both because he's clearly ripping you off, and because the sword may tip the overall greater balance of power (in both Oblivion and the Aedric Realms) in his favor, which would naturally result in a war that would destroy the world. In combination with Azura's Star, it is unarguably one of the most useful items ingame, as the sword—in addition to high attack power—is enchanted with a potent 60-second Soul Trap that will trap the soul of anything previously struck by the sword itself that is either felled or dies. Taking the sword effectively leaves the quest open indefinitely, and the demon-dog-statue-thing will remain in your inventory and can't be removed. Arbitrarily, if the player chooses to take the Masque, the sword is, of course, Lost Forever. This quest entirely subverts the concept of absolute, 100% Completion for the entire game.
 * Most of the better quest rewards are levelled to your character (as well as gold rewards, but this isn't much of a problem), unfortunately these reward items do not scale with you as you level; the item you get is the one you're stuck with throughout the game. Higher-level versions of these items are completely unobtainable if you complete them at lower levels.
 * In The Elder Scrolls III: Morrowind, the unique artifact Spell Breaker can only be obtained if the player is a vampire, meaning that if the player was a vampire but has been cured OR has become immune to disease via the Main Quest, and has not yet obtained Spell Breaker, it's gone. You don't lose it just by getting cured of corprus in the main quest and being therefore immune to common disease, because you can make a custom spell with "weakness to common disease on self" effect and cast it.
 * The expansion Tribunal forces the player to do this for the main quest. You see, the head of the museum has part of an Infinity+1 Sword and she won't give it to you until you donate two artifacts. They can be any artifact (like ones not suited for your character), but they are still lost forever. Unless, of course, you're sneaky enough to swipe them off the museum's displays (and smart enough to not try to sell them back!)...
 * The Elder Scrolls V: Skyrim
 * Prior to the 1.4 patch, the Thalmor embassy was home to a rare gemstone called a Stone of Barenziah, and visiting the embassy without claiming the stone prevented you from completing a quest which required you to find all 24 of them. The 1.4 patch remedied this by moving the stone into the cave you use to escape the embassy, which can be revisited.
 * Skuldafn Temple, a dungeon visited during the main questline, contains a word wall and a unque Dragon Priest mask, both of which can be lost since Skuldafn can only be visited once.
 * The quest involving Potema the Wolf Queen is split into two parts; first you interrupt the ceremony where a gathering of necromancers attempt to resurrect her, then you have to kill her for good. The second part will only trigger when your character levels up, so its possible to lock yourself out of this quest if you hit max level (81) before finishing the first part.
 * In Neverwinter Nights 2, most locations and related sidequests become inaccessible in Act III; even the titular city of Neverwinter effectively shrinks from three districts to one. Some NPCs, however, are relocated to different areas, mostly plot-critical ones.
 * The Xenosaga series mostly avoided this in full; despite that you couldn't actually return to most areas after having visited them, there was an Environmental Simulator where you could pick up things. However, this only worked (for the most part) with combat areas; in the third game, for example, there's a small sidequest that can be missed. In addition, the first two games have extremely useful items that either have an extremely low drop rate or have to be stolen from bosses.
 * Xenosaga Episode I also had the e-mails, some of which were very unlikely to be found by playing the game normally, Guide Dang It!. Not only were many of them Lost Forever once you'd gone past them, but missing one would often make it impossible to get later e-mails, as well.
 * In EarthBound, an enemy in the Stonehenge base Randomly Drops a character's Infinity+1 Sword (and his only weapon, actually). When the base boss is defeated, all enemies in the base disappear and the sword is Lost Forever.
 * Likewise, Ness's Infinity+1 Sword (at least the one of the two that actually works), can only be found on one enemy. In one area. This enemy only appears in the immediate area before the final boss, making it almost useless, especially since you are past the Point of No Return.
 * Star Wars: Knights of the Old Republic contains a fairly egregious example: as you progress through the game, with little to no forewarning, and all items and sidequests therein are rendered Lost Forever.
 * There are also smaller and more numerous examples such as a runaway girl found on your ship, that will eventually run away again and be left to her own fate if you don't finish the 'side-quest' within the time limit.
 * Averted in Paper Mario: The Thousand-Year Door. The game records every time you "tattle" on an enemy (a turn-costing move that lets you see its HP and other characteristics). As some enemies (most notably bosses, but there are others) can't be fought after a certain point, this would normally be a Lost Forever if you didn't tattle on them... except getting those that are Lost Forever is as simple as checking a particular trash can in the Hub Level / First Town.
 * Except for the Mini-Z-Yux, Mini-X-Yux, and at least two other entries forever, as they never appeared in battle due to the enemies being beaten too quickly.
 * Played straight with the Whacka Bumps.
 * Also played straight in the first game. There are a few Badges found in Peach's Castle. You can either collect these with Mario at the very end of the game, or nab them with Peach during her mid-chapter segments and place them in a treasure chest so that Mario can obtain them at a different location. However, if Peach grabs these Badges, but doesn't place them in the chest by the time her Chapter 6 segment is over, they are, of course, Lost Forever.
 * It's played straight with a few items in the Palace Of Shadow. If you defeat Gloomtail and then set off the next event without going behind him and blowing open the crack in the wall, the stuff in that secret chamber will be inaccessible due to the floor to his room dropping way to low to reach the door. Thankfully the only items that can be Lost Forever this way are an Ultra Shroom and Jammin' Jelly, which are generic albeit powerful healing items that are infinitely purchaseable from a store for an expensive price. Your inventory is also likely filled with many of both items or their superior combined form, anyway, so it isn't a huge loss even utilitarianly, in addition to completionary.
 * In Mario & Luigi: Superstar Saga, the Piranha Bean and Piranha Suit are mutually exclusive, making it impossible to get all of the equipment in the game.
 * Shadow Hearts switches the entire map from China to Europe around the halfway point. Everything in China? Gone for good, because you never go back. Oh, and you can't go back to places you leave while you're in China, either.
 * Shadow Hearts also had the Amon fusion. This fusion is obtained from a boss and requires finding a certain item (in the same dungeon, but not located in a chest) before reaching him. If you kill the boss first, you lose access to it. Moreover, the Seraphic Radiance fusion requires Amon and an item from China that is also not located in a chest.
 * Thankfully averted in Shadow Hearts: Covenant, where only two areas are removed from the map after completion - everywhere else can be returned to, and those two areas have a grand total of one irreplaceable item between them.
 * In Shadow Hearts: From the New World, no area ever vanishes, preventing you from losing access to the items within. However, there are Snaps - using Johnny's "Snap" ability on enemies to get their picture. For the most part, you can either trade for Snaps you miss or take their pictures in Lovecraft's Pit Fights. But if you fail to snap, you'll never have the chance again.
 * In Rockman.EXE Transmission / Megaman Network Transmission, if you didn't get the golden Mystery Data from the data graveyard before defeating Zero, the Zero chip is Lost Forever.
 * While the main series normally averts it, there is one instance in the second game. If you don't buy gifts for your friends while you are overseas (easy to miss) you can't return and buy them (even though you can return to the location) but none of the thanks yous are unreplacable if you look enough.
 * Other than the above, the main series itself goes out of its way to avert this. Every boss has a stronger version which you can rematch an unlimited number of times and can drop any Battle Chips its weaker versions can. From the 4th game onwards, weaker enemies in earlier areas are replaced with their stronger counterparts once you get far enough, but a few select areas will retain the weaker enemies so that all variants of all enemies can still be found.
 * In Battle Network 4, the mystery data contain different items depending on what playthrough the player is on. Moving on to the next playthrough without picking up all the blue and purple mystery data can cause the player to miss a HP memory or Navi Customizer part forever. This also applied to green mystery data, which made certain chips such as Wideblade S and Longblade S more easily gettable on certain playthroughs, but virtually impossible on others.
 * Mega Man Legends has the Bomb and Plastique, which are hidden in the city as part of a sidequest. If they explode, you lose them forever - although the Buster parts made out of them are easily outclassed.
 * In Phantasy Star III, there are stores in Cille and Shushoran that sell Star Mist and Moon Dew. But the player can only access the stores in the first generation. These stores are destroyed at the start of the second generation.
 * This is averted in Neverwinter Nights. At the Temples of Tyr, there is a summoning pool, where any unique or quest-specific item can be found for a small fee. Which only makes the trope's presence in the sequel all the more unforgivable...
 * Neverwinter Nights also had companions who would tell you their life stories as they adventured with you (read: once you reached a certain level), and eventually would give you a special item in exchange for something related to their backstories. However, you could only find these special items in the first chapter, and they vanished once you moved to the second chapter. If you didn't adventure with every single companion in the first chapter enough to make the trade, their items were lost forever. Chapter two has them reveal a second part of their backstory and give an upgrade to their item, but only if you received it in chapter 1. You can get another upgrade in chapter 3 - but you can be below the level required by the end of the chapter.
 * Valkyrie Profile 2 has an interesting variation of this that also combines it with Level Grinding and Guest Star Party Member: several characters leave the party as the game progresses, but you also get various items when they do depending on their level, with the best rewards if you grind them to level 40 or 45 depending on the character, while you'd normally be around level 20 or so at that point of the story. Most of these items are unique and generally very powerful, effectively making the transition from Level Grinding to Disc One Nuke.
 * Anything in Zeal in Chrono Trigger.
 * Not to mention opening the sealed chests in the Middle Ages before opening them in the Present.
 * You can take the Swallow or the Safe Helm, but not both. Same with the Prism Dress and Prism Helms.
 * Take the Swallow. Completing a side quest allows you to buy Safe Helms.
 * Actually, you can Charm a Safe Helm from the Lavos Spawn's shell aboard the Black Omen, and later on that same dungeon, you can grab one each of both Prism items by Charming hands. As a bonus, if you do things right, you can fight the latter boss up to 3 times in the same file, meaning you can potentially have an almost-full set of Prism gear (you'll be short a Prism Helm if you got a certain optional character, but said character can get a slightly better helm anyway).
 * You can get Magus to join your party, ONLY if you refuse to fight him at a certain point. If the question presented didn't already seem like a "But Thou Must!", his boss theme plays while you make the choice, basically telling any Genre Savvy player that there is no point in saying no... except that there is. And in the DS version, you can only get his Bestiary entry for this fight if you do kill him... which, of course, means he can't join your party unless you do another NG+.
 * This happens in Chrono Cross, too. There's many a time when making a choice that enables you to get one character will result in you losing another: for example, opting not to save Kid at Guldove will let you recruit Glenn, but any chance of recruiting Razzly is—you guessed it—lost forever. There's a New Game + option that seemingly makes up for this, but it only becomes available about halfway through the game.
 * It's VERY easy for Razzly's Level 7 ability to be Lost Forever too. Fight an adjacent boss with her in the party? Fail to witness tragedy? Good bye Raz-Flower. And the most powerful combo attack (Infinity plus one spell?) in the game.
 * Say yes to Kid when she first offers to join? Well you just lost Leena. Answer one or both of the questions she asked earlier wrong? Well, you just lost her best tech.
 * In Fable I, there's a very special weapon in a key chest in the Heroes Guild. However, if you do not obtain all the necessary keys or just procrastinate in opening the chest before Jack of Blades attacks the Heroes Guild, the weapon is, you guessed it...
 * This gets fixed in the expansion pack, as you can revisit the (rebuilt) Guild after the attack. Later in the game, you may encounter a demon door that demands all your keys to open, which would make all the contents of the chests you haven't opened yet Lost Forever... but you're given ample warning, and it's optional.
 * Another demon door requires you to find three suits of armor, the first one being bright plate mail. Unfortunately, it's only sold in the Arena; and you can only visit the Arena once, at a specific point of the main quest. So if you didn't buy all its parts, at the one and only possible time, you can never open the demon door. (This is also fixed in the expansion, where you can buy the armor in one of the added locations.)
 * Yet another door can only be opened if you had married the villainous Lady Grey. If you choose to expose her evil deeds instead (only possible in the expansion), you're out of luck.
 * Or if you become Mayor in the Fable: The Lost Chapters, by turning her in. Ideally though, one should court her, fight Thunder (it is an area off limits and only accessible if you fight Thunder for Lady Grey's favour), then turn her in (find her dead sister).
 * Fable II only has one (potentially avertable) instance of this. If you However, if you have the Knothole Island DLC, then.
 * It's fortunately only a small item that is perfectly fine to miss, but in near the beginning of Super Mario RPG there's a part where Toad is walking into the castle. In order to get a certain hidden block, you need to jump onto his head at just the right moment and use the additional height to jump and hit the hidden block. You only get one chance at this, and the only way to know it's there (other than using a guide) is to have an item that you get significantly later in the game.
 * Which in itself is kind of sadistic because the item only lets you know a hidden chest is in the room, it does nothing to help pinpoint the location. The room is rather large too so without using a guide, you'll be left jumping in every inch of that room looking for a hidden chest that is in a place you not only can't possibly reach any longer, but is in a place you have no idea you even CAN reach because you never do anything like that ever before or ever again.
 * The game also features
 * Averted in Lost Odyssey, thankfully. Items from areas that cannot be returned to become available in an auction house that exists for that sole purpose. Even if the player loses the auction for an item, it will reappear until the player wins it; winning items this way is sufficient for One Hundred Percent Completion.
 * Given that to get the 'all items' achievement requires nearly 700 items, literally hundreds of which are in items almost indistinguishable from mundane items and are usually overlooked, dozens hidden in inexplicable places or that require incredibly hard puzzles to get to, about 50 from sidequests ranging from easy to merciless, 24 from following vague clues to hidden items and 11 that are literally invisible with no indication that they're there, and something like 70 of these items can be missed, being able to buy what you miss is only fair.
 * There are two spells which can only be purchased from two different vendors. One is in an area at the end of the second disc, the other is in an area near the beginning of the third disc. Each of these vendors are in areas that once you progress far enough, can NEVER be visited ever again. Granted, you get more powerful versions of these spells later (and they aren't permanently missable) but you could still miss out on an achievement this way.
 * Once the four primary planets in Mass Effect 1 have been finished, you automatically return to the Citadel, where several new sidequests become available....and then you hightail it out of Dodge and cannot return to the Citadel  for the rest of the game. Fortunately, there's only the final planet left to complete after this point anyway.
 * Also in Mass Effect 1, there are Achievements you gain from having certain party members in your party for a certain percentage of the game. However, since you only get Liara once you leave the Citadel for the first time, and the planet she's on is only one of many you can visit, it's possible for there to not be enough game left to complete once you get her, locking you out of the achievement until the next playthrough.
 * Liara's Achivement is nearly a Guide Dang It in the way you're better off beelining to recruit her, avoiding any optional quests until she's part of your team. The precise amount of main and side quests completions required for the achievement is different for each party member, depending on which point of the game you can recruit them, but the margin of error is less for later characters.
 * The also offers several sidequests which can be Lost Forever if the hero ends up killing the characters associated with them - nice job, Shepard.
 * Several side quests and subplots are potentially continued on in the next two games. Lost Forever times three. Oh, and the skip dialogue button can also choose dialogue, so it's possible to accidentally choose something you didn't want by accident.
 * In Mass Effect 2, most weapon and armor upgrades can only be found during missions. Thanks to the game's rigid mission structure, there's no way to revisit the locations of missions you've already completed. Complete the mission without getting the upgrade, and you're outta luck. New Game+ mitigates this somewhat.
 * Additionally, there are three separate mini fetch quests you can perform on Illium where you can find an item or information significant to a separate NPC. These can only be found during Miranda's loyalty mission, Samara's recruitment mission, and Thane's recruitment mission. if you don't find these items during their respective missions, you can't complete the fetch quests.
 * In Mass Effect 3, once you complete Priority: Tuchanka, several side quests on the Citadel will become locked out if uncompleted. Additionally, if you wait too long to complete two side missions ( and  ) after they become available, they will be considered failed, locking you out of the relevant upgrades and war assets.
 * Also in 3, you regularly find new weapons during missions. Most of them can be purchased at the Citadel if you miss them, but two weapons, the M-358 Talon and the M-99 Saber, have to be found during missions or else they become unobtainable. While none of them are mandatory to complete the game, it's always nice to add a new gun to your arsenal.
 * In Kings Field II, a certain merchant, sells a number of dead useful items, but at the time, they seem rather expensive. It's only until later one realized that a) many of her wares are otherwise unattainable, and b) her prices are actually quite low. Of course, by then.
 * Marvel Ultimate Alliance allows you to return to almost any area you've already completed, but there are a few exceptions, such as the SHIELD base in Atlantis or the fake Dr. Doom's castle in Murderworld. Any items missed there are gone until your next playthrough.
 * Breath of Fire 3 has the Beast Spear, a weapon for Garr. It has far more attack power than any of his other weapons (his next closest weapon is a good 40 points weaker than the Beast Spear), though it also weighs a lot and drains a bit of his HP every turn, which for some makes it Awesome but Impractical. Anyway, it can only be obtained by examining the ashes of a Duel Boss before leaving the room where you fought him. Take one step outside, and the weapon is gone for good.
 * Soul Blazer wants you to find these 8 Emblems. If a Dolphin who would've cheerfully given you an Emblem when he was asleep had, regrettably, woken up, then good-bye, Magic Bell.
 * Thanks to a glitch, the Mock species in Monster Rancher 2 can become lost forever. You get the Mock by randomly receiving some seeds from the item store after getting a monster to Rank B. There's no guarantee of when you'll get the seeds; you have to keep visiting the store. However, if you get a monster to Rank A without getting the seeds, you'll never be able to get the Mock.
 * Obscure Game Boy Color RPG Lil' Monster has the Dowser and Dragonscale ability gems, and their associated monsters, Gyro and Argon. These two monsters are fought as bosses. However, the bosses will only appear once, and if you lose to them, they'll vanish. You'll never be able to get their ability gems. Frustratingly, missing Gyro/Dowser also means you miss the Disc One Nuke, Minhand, which doubles your attack power, as the monster that holds that particular gem only appears when you use the Dowser gem to summon a monster to fight.
 * Near the beginning of Infinite Undiscovery, Sigmund gives you his sword. It's nothing special and the Sorting Algorithm of Weapon Effectiveness makes it useless fast. As a further temptation, it does sell for a pretty high price for such an early item. If you sold it, say goodbye to the Infinity+1 Sword.
 * In Wizardry Tale of the Forsaken Land there is an NPC on level 1 of the dungeon who you can play various minigames with, most of which give you very rare and useful items upon completion. Each game is harder and more rewarding than the last and you can replay them as often as you want... until you beat the main quest, at which point the NPC, and for that matter any uncompleted quests in the game become completely inaccessible. However you can now access the secret bonus dungeon, which was right behind the minigame NPC all this time.
 * Averted in Phantasy Star II, if you accidently put the visiphone in, you can simply have Shir steal another one.
 * The Flail of Many Heads from Baldur's Gate II was available as a sequence of components early in the game, which weren't too difficult to find. However they could only be assembled in that one location, which upon completion was locked off forever unless you had chosen the right character class at the beginning of the game (the beginning of the previous game, if you'd continued with the same character!) Particularly galling since there was a shop specifically for the purpose of assembling such items, but the shopkeeper ignored the Flail components, so it would be entirely possible to lose the item while trying to get it assembled.
 * In the expansion pack your butler could put the Flail together for you, but since that required you to carry around three useless but valuable items (which took up three times as much space as a weapon which actually worked) for the entirety of the game- when you weren't even aware the possibility existed- not many players took advantage of this.
 * Also, certain dungeons (The Planar Prison, the Sahaugin City, etc.) cannot be returned to once you leave them, and any items contained therein... well, you know.
 * Age of Pirates 2: City of Abandoned Ships is mostly a sandbox game, but it does have two of what you could call main quest lines, one for one of the nations and the other for the pirates. You can do both, but only if you finish the national quest line first. If you even talk to one of the pirate bosses the governor general will refuse to give you missions because of your ties with pirates (nevermind that you keep sinking their ships left and right). That means you will never be able to access some of the game's features, such as the ability to capture towns, that are only unlocked during the national quest line. You are of course given no prior warning or afterwards notification whatsoever that you're being screwed over like that, on the contrary, your character gushes like a schoolgirl in both conversation and journal at how great it is to be given an opportunity to work for the great pirate lord Henry Morgan. Hm.
 * Fallout 3 has collectible bobbleheads that increase your stats. Four of them can be lost forever: Strength is in ; Energy Weapons is in ; Medicine is in ; finally, there's Repair, which is in.
 * Non-storyline quests can also be lost forever if you murder someone crucial to the quest. Of course, if you kill random civilians for fun, you probably deserve it.
 * Also averted for the  quest; if you  will survive, though  now a Ghoul.
 * Potential party members can be killed before you have the chance to let them join you. You can murder Butch within five minutes of getting a pistol, for instance.
 * When it comes to the 4 major DLC in Fallout: New Vegas (Dead Money, Honest Hearts, Old World Blues, Lonesome Road), you can return to any of their areas as often as you like upon their completion, with the exception of Dead Money's Sierra Madre. Once you leave, you can't return, unless you use console commands in the PC version.
 * As in Fallout 3, potential companions can be killed in New Vegas. Unlike Fallout 3, though, some companions are found outside, where they're at the mercy of whatever may wander in. A particulary bad spot is Jacobstown, where you meet Lily, which happens to have a Cazadore spawn point near the front gate.
 * Thankfully averted in Wild ARMs 3, where a Bonus Boss needs to have every chest in the world open to fight him. Luckily, no chests were placed in any one-time dungeons. Unfortunately for Wild ARMs 4, which has the same boss, that's not the case.
 * In Wild ARMs 2, Marivel is needed to find the Fab Science Lab, while inside, you battle and afterwards, you'll see an hourglass-esque object appear,, you'll have to switch to Marivel and check it to get it, people are known to exit the dungeon without doing this and so the hourglass vanishs preventing you from a 100% game.
 * In Sword of Mana, several Lost Forevers include an item only acquired with certain skill sets, characters who when killed while holding your gear, or just leaving you to return later loseing your items (bad if the above skill item) and not going back after most sections of the game, remedied after Dark Lord's castle, but then getting a lost forever on all quests and new items after entering Dime Tower.
 * In Dragon Age pretty much all of your party members except Alistair and Morrigan can be lost to the ravages of this trope if you are not prepared to do the new character quests at the earliest opportunity.
 * You can even accidentally choose to kill a potential party member instead of recruiting him. D'oh!
 * When you first arrive at Lothering, two possible companions are available. If you leave Lothering and complete one of the main quests without having picked them up, it gets destroyed by the darkspawn, and you lose any quests, loot and potential party members forever.
 * Another rather annoying example is in the Human Noble origin. If you don't go to the treasury to pick up the powerful "Family Sword" weapon before escaping the castle, it's gone for good (along with all the treasure chests that you couldn't open if you chose Warrior instead of Rogue).
 * Dragon Age is actually full of these. Random encounters and sidequest levels are often impossible to enter after the corresponding quest is solved, leaving the loot one has not picked up inaccessible. As the party inventory is far from infinite, sometimes the player will find himself unable to pick everything up without destroying some of his valuables.
 * It is worth noting that these items are vendor trash that solely exist to be sold for relatively small amounts of money. None of these items are anything you would go back to get anyways.
 * A minor but rather annoying example appears in the "Return to Ostagar" DLC. If you already looted the Magi encampment chest using the key the Hungry Deserter gave you, you will miss out on the rather powerful Corrupted Magister's Staff. On the other hand, the DLC also gives you another chance to recruit Dog.
 * The unique items that appear randomly on certain enemies/chests are Lost Forever if you don't get them and overwrite the saves before fighting them/entering the area they appear.
 * Near the end of the Awakening expansion, the Darkspawn lead two seperate attacks against the player, one on the city on Amaranthine and one the Warden's base, Vigil's Keep. The player has to choose which to save, and if you choose Amaranthine any party members currently stationed at Vigil's Keep will die in the attack. It is possible to save both Amaranthine and your soldiers at Vigil's Keep (though the keep itself is still rendered unusable for the rest of the game) but doing so requires the player to complete a lengthy sidequest that involves, among other things, collecting ore deposits. Said deposits happen to be located in places you can't return to after leaving, which means if you don't get them the first time you're there you can't finish the sidequest (and by extension, save your party members).
 * Dragon Age II is full of this. The game is split into three acts, and any quests, treasures, party members, etc. that you don't get in one act will be unobtainable in the next. It's also possible to miss or lose every party member except, depending on your choices. Finally, certain areas and dungeons are inaccessible as soon as you leave them.
 * Golden Sun: Dark Dawn has this with permanently missable djinn and summons, the former having an incredible 35 potential missable spread over three different points of no return, out of 72 total djinn. Particularly irritating in that some of these djinn and summons have very small windows of opportunity to get them, and there wasn't anything like this in the first two games. The Ninja Sandals equipment is also lost forever if you don't talk to a certain NPC the first time you're in Kaocho. Additionally, some Encyclopedia terms can be lost forever if you don't talk to random NPCs in the Morgal region, frustrating those who consider filling it out as part of 100% Completion. Even more irritating, oftentimes those terms WILL appear in other characters' dialogue, but they're not highlighted in red, so it doesn't count.
 * The female protagonist's route in Persona 3 Portable has two Social Links that are only available for one month each. If you fail to complete the Moon link in September or the Fortune link in November, they (and the powerful Personas that they enable access to) are gone for good.
 * Even back in FES, it's easy to forget to confirm that you've taken Elizabeth (or Theodore in Portable) out on a date to obtain key items to fuse certain Personas before the quest's deadline.
 * There aren't a lot of these in Opoona—the biggest ones are a pair of artwork in the Artiela Museum (if you don't view them right when they appear, you won't be able to add them to your Artbook), and the friendship of Ine. First, you've got to make sure you can play the ukelele by a certain point in the game, or else you'll miss friendship with her. Secondly, another character will give you an item that you can sell for lots of money, but you have to give it to her to both cement her as a friend and to get an item that's necessary later on for increasing the friendship of another one of your friends.
 * In Dark Souls, you lose the ability to join the Darkwraith covenant if after getting the Lordvessel you speak with Frampt before joining it. Fortunately there's always the next playthrough.
 * In Arcanum you get a very limited window of opportunity to recruit the Dog into your party, who is one of the strongest melee combatants in the game, needs no items, wields no weapons and thus suffers no durability damage, no matter what he attacks. The recruitment window is limited because as soon as you arrive in Ashbury the Dog's introductory event begins. Unfortunately, that event involves a halfling kicking the Dog while it's down and there is nothing to stop the Dog from dying this way. If you don't immediately run over to the halfling after arriving at the town and chase him away, the dog will die and you will never get another chance at recruiting him. It is virtually impossible to know this on your first playthrough without consulting a guide of some sort, leaving it entirely up to luck, wether you by chance go in the right direction to encounter the halfling in time to save the Dog or not.
 * Another significant thing that can easily be Lost Forever are Lava Rocks. There are very few of these items in the game(three or so), all of them found in the Wheel Clan caverns. There is no obvious significance to these items so it is likely that a player will simply sell them after picking them up. Considering that the item stock of most vendors is on rotation this will lead to the Lava Rocks being destroyed once the vendor's stock changes. However, these rocks are the only things that a certain dwarven god accepts as offerings, and without his blessing it is impossible to complete the chain of blessings necessary to gain access to Velorien's blessing of ultimate power, which in and of itself is an unlikely feat without the use of Guide Dang It.

Simulation Game

 * In Freelancer, there is a very good ship called the Anubis that you have exactly four opportunities to obtain: if you don't get it (which is frankly rather silly, as it's dirt cheap) within those four chances, or sell it afterwards, it's Lost Forever.
 * Many of the older Harvest Moon games have items and characters that will become unavailable after a certain amount of time. Most famously is HM64, where Cliff and Karen will leave town if you do not get their relationship levels high enough - depriving you of two potential rival marriages and 100% completion on your recipe list. The death of is avoidable, if you know what to watch out for (If she's sitting on the side of her house, instead of the front, DO NOT APPROACH). But if she dies, she'll take her recipe with her and knock a good chunk of points off Elli's affection levels.
 * Another particularly nasty one is the Hot Springs in DS/Cute, which can only be found by befriending or partially wooing Flora (regardless of whether or not you intend to marry her), since finding it is one of her Heart Events. The problem? If Flora marries her partner Carter, you're locked out of the event forever. In the girl version, it's based on Friendship instead of Affection, but you're still locked out of the Hot Springs-discovering event if Flora or you marries Carter, for seemingly arbitrary reasons. What do you miss if you don't get the Hot Springs? A different Hot Spring in another area of town, a shippable item (the Spa-Boiled Egg), and a huge chunk of Harvest Sprites, making One Hundred Percent Completion of the Harvest Sprite teams impossible. On top of it all? The whole thing is a Guide Dang It.
 * The hot springs actually unlock automatically after your child is born as an alternative method. Of course, in order to get that far you have to get married, which you can't do before finding 60 Harvest Sprites and freeing the Harvest Goddess. As the Hot Springs is required in order to find a decent portion of said Harvest Sprites, it's needless to say that this task is much easier to accomplish if you already have the hot springs, which makes doing all of this just to unlock the hot springs you know what my head really really hurts now.

Stealth Based Game

 * The Metal Gear series often averts this. For instance, if the player misses the SOCOM pistol at the start of MGS1, he will have one sitting in front of him during the first major firefight. In MGS3, if the player fails to locate the Night Vision Goggles in the cavern, EVA will simply hand him a set in a later cutscene, etc.
 * There are still some items that can be Lost Forever, particularly optional items, if they are not picked up as soon as they are available. Examples include the torch from MGS3 (find in the cave before The Pain boss battle or never again) and AKS-74u silencer in MGS2. Neither are overly necessary and both actually require more effort than just leaving them, but for 100% completion...
 * The Twin Snakes has a silenced, tranquilizer-shooting M9. On nearly all difficulty levels, it's hidden somewhere in the Cave area. The cargo elevator at the back of the Cave is a one-way trip.
 * In Metal Gear Solid: VR Missions, if the player completes all the training missions, the game will show a concept artwork of Metal Gear RAY from the then-upcoming Metal Gear Solid 2: Sons of Liberty. However, there's no way to view picture again once the data has been saved.

Survival Horror

 * the Fatal Frame games contain quite a few ghosts that only appear once, for a very short period of time, and are often very difficult to capture on film unless you know exactly where and when they will appear and have a lightning-fast shutter finger.
 * In Silent Hill, there are many points of no return that can render items and weapons missable, for example, during the fight with the Twinfeeler (caterpillar, which later becomes a moth) boss, there is a rifle (may be required for the Final Boss) in one of the corners of the fighting arena. If you didn't happen to notice it and pick it up, it will never be available again. Similarly, there is a sledgehammer in the Nightmare Hospital boiler room, which will be Lost Forever once you go back to the "normal" world. And God help you if you passed a Point of No Return without enough ammo or health to fight the upcoming boss.
 * The first game will actually reward you for entering the final boss fight with no ammo.
 * And if you didn't get the red liquid in the bottle in the hospital, kiss Cybil and the Good+ ending goodbye. If you didn't unlock the motorcycle gas tank in the motel before you traversed the Point of No Return into the nightmare resort area, say goodbye to the Good ending too.
 * In Silent Hill 2: There's a pipe in the hood of a car at the gas station, and if you're rushing around a lot or don't know to pull it out, you can easily hop down the hole in the Silent Hill Historical Society and not have anything to smash a hole in the bricks.
 * You can break the bricks in the well with the wooden plank, meaning the situation isn't unwinnable. The steel pipe is still unobtainable from that point, though.
 * Silent Hill 3: if you missed the stungun in Heather's apartment or the submachine gun in the hospital basement, ya missed 'em for good.
 * Silent Hill 4 completely averts this by supplying halfway into the game the 'Ever Downward' spiral staircase, which vertically connects all levels in the game, allowing for all the backtracking it takes to retrieve missing items such as the Swords of Obedience and all two Silver Bullets.
 * In Resident Evil: Code Veronica there's a section of the building that is  only accessible through a functioning metal detector gate which essentially puts the area on lockdown if you don't get rid of any metal items from your inventory. Fortunately there's a sort of baggage check compartment built in. This container is not connected to the other chests throughout the game. Remember to take everything out when you're done with that part, because "leaving town" doesn't begin to cover it. Of surprising significance:.
 * Near the end of Code Veronica, Claire becomes playable until you encounter Steve for the last time. Whatever items or weapons she's carrying will be lost forever when you switch back to Chris near the end of the game.
 * Resident Evil 4 features missable treasures in various parts of the game. While any treasure becomes lost forever if you move on to the next section of the game, the combine-able treasures (beer stein, crown, and golden lynx) in particular are likely to be missed as well as their smaller parts. While this doesn't make the game Unwinnable it does prevent you from making lots of money and thus delaying your weapons progression.
 * Resident Evil Outbreak had an online mode hosted on Capcom servers. Because the game was a commercial flop, Capcom closed the servers and much of the game's features are Lost Forever.
 * In RE 2, any optional item before the Laboratory is missable, such as the Sparkshot(Claire) and Shotgun Parts (Leon), which are found on a corpse in an easily-missed dead end, the Weapon Box Key found by lighting an easily-ignored flare gun (with the Lighter that Claire doesn't automatically carry), and finally, the Sidepack and Submachine Gun(which you either find in the Weapons Room, or the Culture Experiment Room that you have to unlock with both characters).
 * Eternal Darkness had runes et cetera that would not be necessary in one level, but would be needed in another, the Lost Forever rune made the game Unwinnable. Most notably, the game has three different colors of magick - red, green and blue, which beat each other in a Rock-Paper-Scissors cycle. There actually is a purple magick color, the rune of which can very easily be Lost Forever, and any purple magick defeats any other color.
 * Deadly Premonition has sidequests and collectible items that appear and disappear throughout the game, sometimes for what seems to be very little reason. It's extremely easy to check too early or late and thus miss out on a sidequest, which then never shows up again.

Turn-Based Strategy

 * In Final Fantasy Tactics Advance the morpher class requires captured monsters to learn skills from. The goblin and thunder drake monsters become Lost Forever if not captured early on as they only appear in non-random storyline missions and so become "extinct" after those missions are completed.
 * Doesn't help that they're two Lost Forevers in one - not only do they need to be captured so that Morphers can become them, but they also teach Blue Mage abilities - and they can't be learned from Morphers.
 * Thanks to the limit of holding only 64 mission items, it is possible to keep throwing away extra mission items when you are full (most of them you can get again and again) and wind up accidentally tossing away an item that cannot be obtained again. What's that? Two missions need Black Thread and you tossed one of the two away? Can't complete all 300 missions and can't recruit Cid. Oops!
 * Thanks to enemy thieves, mog knights, and snipers, you could potentially lose some of your exclusive equipment forever due to it being broken or stolen. The purple turtle enemies also had the ability to break your equipment by eating it.
 * Final Fantasy Tactics generally averts this trope, since many unique weapons and items that appear early on in the game can be acquired later through poaching, or by catching thrown items. However, there are items that can only be obtained by having a character with the Move-Find item skill land on a certain space. Depending on your character's Bravery level you may either find a rare item or a common item. Since an item can only be searched for once, finding the wrong item in battle may result in the item becoming lost forever. Also, since some maps can not be revisited, you may have the chance to miss the item altogether.
 * One of the most insidious Lost Forever items is the Snakish sword in Phantom Brave. It can only be accessed once: during the tutorial. And, thanks to the game system, you can't just pick it up and leave with it. You have to confine a spirit to it and wait until the spirit is removed from the board, and even then you're not guaranteed to get it. There is a more sure-fire way to get it, but it's by getting a hidden character, and the opportunity to get that character is all but impossible after that section, making that a Lost Forever too.
 * In every game of the Suikoden series, while most of the 108 recruitable characters either join automatically over the course of the story or can be recruited at any time, some have limited windows of opportunity, after which they're Lost Forever. Since recruiting all of them is required to get the best ending, and on top of that these characters tend to be very easy to miss, the result is the definition of a Guide Dang It situation.
 * One particular example in Suikoden II is the Clive subquest. He's chasing after a woman. Easy enough, let's help him out. If your total play time is too high, then he loses the trail and will never find it again, giving him the "bad" ending for his character (he chases her for pretty much the rest of his life). The problem with this is two fold: first, there's no indication that this will happen at any point, meaning if you lose the trail, you'll have no idea why without a guide. Second, in order to fully complete his quest, you have to reach the last possible village in the game (which is, itself, optional) in less than twenty hours play time (not the easiest accomplishment even if you know from the start to try for it). For most gamers without a specific guide for recruiting characters and level building, this is all but impossible.
 * Thus, most players either don't bother with Clive's subquest (as it's immaterial to whether you get the best ending for the game as a whole), or they cheat.
 * The same thing is true of the old Genesis Shining Force games, including one character that you have to speak to over several acts, who never says anything back. However, these characters are not necessary for the overall story or endings, but the characters you could prospectively lose include Joke Character, a defied examplle of Squishy Wizard, the game's best Tank and the two best characters in the game, who are difficult to find without the help of a strategy guide
 * Another batch of potential things to Lose Forever was introduced in the GBA remake...cards. Some cards are tucked away in inconspicuous places; Anri's is in a bookcase, and most bookcases in the game simply call up useless flavor text when examined. Others, however, are nicknamed "Friendship Cards" in that you have to build rapport with certain party members to get them. How do you build this rapport? Simple: bring the character in question with you into battle and make sure they never get KO'd; this unlocks more and more of their monologues in headquarters between missions, and eventually they say something to the effect of "take this; we're friends" and reward you with their card.
 * In the same vein as the above "Friendship Cards", certain enemies have to be finished off by certain characters. A particularly Egregrious example is Balzack, who has to be defeated by a knight named Earnest (who, it should be noted, you just recieved prior to the Balzack battle. Granted, this makes sense, since Earnest pretty much exists to Wangst over his beef with Balzack; on the other hand, the mission immediately before that asks you to eliminate a random Hellhound with Guntz. God Light help you if you didn't even recruit Guntz...
 * Well, at least you had as many New Game+-es as you needed and could keep your cards for every playthrough. Only problem is that the difficulty was raised each time.
 * Several of the best (or coolest) characters (and one Joke Character) could be missed without ever being seen if you took the direct route over the scenic route. These included the Ninja, Samurai, magic-wielding centaur, healer/monk, mutant egg creature, and a hamster.
 * In Advance Wars 2 and Advance Wars Dual Strike, certain levels have cities that, when captured, unlock a bonus mission. If you clear said certain levels without capturing said certain cities, the bonus mission - and the prize for completing it - is Lost Forever...until your next playthrough at least. While the game hints at which levels have these cities, you don't know which city out of several is the one you need to capture. Although...it's up to the player whether or not the prize for completing the bonus missions (The ability to deploy Neotanks) is actually worth the work.
 * Since you cannot replay missions in the Fire Emblem series, this goes for everything and almost everyone that is not automatically given to you. Often in ways of Guide Dang It. Watch out for items hidden in deserts or for chests in stages with enemy thieves.
 * In Genealogy of the Holy War, not pairing up the 'right' people in the first half of the game can result in certain weapons becoming unusable or downright lost.
 * There are only three characters over the course of the series (read: Twelve Games!) whom you have more than one chance to recruit. You have two chances each to recruit Amelia in Sacred Stones and Percival from Sealed Sword. Cath/Cass from Sealed Sword will appear in every indoors map until you recruit her, but Roy must talk to her over three chapters for that to happen.
 * They pop up on occasion in Battle for Wesnoth. Capturing certain villages or visiting certain areas in campaign mode will give you free units which usually have no upkeep cost. These can be very useful in some campaigns. On a couple of occasions (the three Heavy Infantry and Burin from the Rise of Wesnoth), missing them renders the whole campaign basically Unwinnable.
 * In both versions of Yggdra Union, pretty much every item save for starting equipment is missable. Everything requires you to have done a lot of searching and hope that you can find something before you run out of turns.
 * To top it off certain items can only be acquired through various means. Many items require you to have fought and killed them with higher luck, others require you to steal it (your luck should not be high enough to force a drop), others still require you to have done something in previous maps and the oh so impossible to find Fanelia weapon which requires you to have acquired the Hyper drill by collecting 7 hard to find duds (and in the process missing out on certain equipment in the old game unless you saved and reloaded) and stepped on a space 3 times to having to kill an enemy with a specific card ability.
 * To make things even worse, in order to even equip Hyper drill(a requirement to get fanelia), Durant must be at the max level in the game(not an easy thing to do)
 * Star Control 2 is full of these. One of the most effective ships in the game is piloted by a race of abject cowards and if you fail to get a supply of them immediately when able, they all disappear under a force shield. Unfortunate and irreversible stuff keeps happening as time goes by and ultimately, if you don't get things done,
 * Some of the dungeons in Eternal Eyes cannot be accessed after you defeat their respective bosses. While in some cases this doesn't seem so bad, some of those dungeons contain randomly dropped equipment that you might want. In particular, Villee Fort (which gets replaced in the tenth and final chapter) has the excellent Ninja Suit in it, which is one of the few equipment that can increase your Movement Points and let you travel farther.
 * Super Robot Wars loves this trope. Every secret in the game is missable, and you aren't ever really told about them... however, most of them are logical and there aren't a lot of variations on how to get secrets, so it usually becomes a matter of trial and error. Also, in the games with Skill Points, it generally becomes a matter of having really high or really low Skill Points.
 * Shin Getter Robo's probably the best example of this. In Alpha and Alpha Gaiden, fans had to choose between keeping Getter Robo G or Shin Getter Robo once Shin Getter appeared (it was the same for Mazinger-Z and Mazinkaiser, but only in Alpha), Impact forced you to choose between Shin Getter Robo and normal Weissritter or Getter Robo G and Rein Weissritter and choosing a certain path in Compact 3 would either net you an unupgraded Shin Getter Robo or an upgraded Getter Robo G.
 * The Linear plotline of all Fire Emblem games tends to make this fairly common. The enemy killed off the only person capable of recruiting some powerful enemy to your side? TOO BAD! You missed out on the secret shop? No going back to it! Sometimes an enemy will drop a unique item. You know where this is going.
 * In Warhammer 40,000: Rites of War, it is possible to find valuable artifacts or other war-gear on the various scenario maps of the campaign. But if you complete a scenario without first finding all the available wargear (and there are scenarios where, given the limited number of turns you have to finish, you simply will not be able to look everywhere), that artifact or piece of gear is Lost Forever.

Turn Based Tactics

 * In X-COM: Terror from the Deep, the Sonic Pistol is phased out by the aliens after a few months. This can screw you over if a) none actually ever spawned during that time, or b) you sold all the ones that did because you didn't know about it. Researching the Sonic Pistol is tremendously important, because it's both the best assault weapon in the game, and a required prerequisite for the Sonic Oscillator, the best craft weapon. It is possible to win without these, so it isn't Unwinnable, but it's a lot harder.
 * This game has a couple of research tree bugs:
 * These two items, the MC Reader and the Sub Construction store item, are special in that they will only become available for research if and only if a sample is available in your general stores before completing research for their prerequisite technologies.
 * Live Deep One, which should only be researched after you have met the other prerequisites for Ion Armour. Without
 * In Odium, combats and exploration are done on separate maps. Sometimes, combat maps contain a crate with goodies or two. If you do not open and empty a crate before killing all the enemies, everything you failed to grab will be Lost Forever. (Though there are never any unique items in there.)
 * Cecille from Luminous Arc has a particularly plot-relevant Class Change that resets her Relationship Values and opens up a new set of related conversations. Any items you didn't get from raising her Relationship Values before her class change are Lost Forever, along with the special CG for maxing them. Really forever, since her class change is retained going into the New Game+. The items can be acquired by other means, but the CG can't.

Visual Novels

 * In Fate/hollow ataraxia if you don't see some of the filler scenes before moving to the plot scenes, they're no longer available. And if you don't get 100% completion you can't unlock a bonus scene.

Wide Open Sandbox

 * Entire missions in Grand Theft Auto (and its GTA: London expansion packs) are Lost Forever if you fail them. When the jobs you're offered start getting... challenging (think assassination attempts on politicians protected by machinegun-wielding bodyguards), let's just say it's a good thing that level completion is tied to your bank account, not storyline missions.
 * In Grand Theft Auto III, it's incredibly difficult to complete the police vehicle missions once you leave Portland  Since those missions are required for 100% Completion, this screwed many gamers who decided to procrastinate on doing them.
 * Additionally, missions where you work for can be lost forever, if you don't complete them before  However, players surprised that  should consider the possibility that they've been playing too much Grand Theft Auto III.
 * Same with Salvatore Leone, whose missions that you didn't complete are lost forever after you assassinate him.
 * On top of that, there was a bug in the PC version that made 100% completion impossible forever on any new games you save. There is a mission on Shoreside Vale where you have to do a drive by on X amount of enemies. If you had completed all the missions for the guy at the phone and attempt to do this particular mission in a new game after saving, the enemies NEVER spawn!
 * Grand Theft Auto IV has what can only be a very intentional variation of the above and for once an interesting twist: there are certain missions where you are presented a choice of whether or not to kill someone. The game is even nice enough to tell you that "your choice has consequences for the future." What it doesn't tell you is that the person whose life you're playing with also has missions for you to do should you choose to spare them; if you choose to kill them, well, that means no extra side-mission for you (and that you're a cold, cold bastard).
 * "The Lost and Damned" expansion has an even more egregious example.
 * Inverted in Bully. Chapter 1 features "The Big Prank" side mission, available only during Halloween night. Unlike every other mission in the game, this one's gone for good if you don't do it the minute it shows up (ie. sleep during Halloween). Which isn't advisable, if you're looking for One Hundred Percent Completion. Fortunately, the game literally texts the uniqueness of the mission and leaves very little margin for the player to miss it.
 * No More Heroes. The collectible cards scattered around in each of the ranking matches are Lost Forever once you finish that level. The first time through is not a problem, since they're just trading cards of fake Mexican wrestlers, but in New Game+, . Of course, you could always just start another New Game+.
 * In The Godfather: The Game there are Thief Bags with cash in every mission that will disappear after the mission is over. Fortunately, it's just cash, which you can easily earn elsewhere.

Comic Books

 * Y: The Last Man: Done via Continuity Nod. During the One Small Step arc, Escape Artist main character Yorick is stuck in unpickable handcuffs designed by Mossad of Israel's Secret Service. A couple of arcs later, we see a flashback of a magic store owner offering him the only skeleton key that works on those cuffs. Yorick must have been kicking himself.

Religion

 * The Bible teaches that most human beings are this. People are "lost" when they sin, in which case they must be "found" (saved) before they die. If they are not, they are permanently lost, with no hope of ever being retrieved.

Card Games

 * Magic: The Gathering: Not exactly Lost Forever, but if you didn't get the Power Nine when Beta came out, you'd better be a professional gamer, or you'll never see the point. Same with dual lands.

Choose Your Own Adventure-type books

 * Absolutely endemic.
 * Fighting Fantasy could be particularly bad about this. In "Black Vein Prophecy" and "Creature of Havoc", you could miss useful items or powers on a dice roll. ("Black Vein Prophecy" was particularly grim, since the dice roll in question was failing a Luck Stat roll.)

Tabletop RPG

 * Dungeons & Dragons adventure WG6 Isle of the Ape. Near the end of the module six jewels worth a total of 300,000 gold pieces float to the ground. If the party doesn't pick them up within one round (1 minute) they vanish forever.

Web Original

 * Any website that doesn't allow the Internet Archive to search its old pages.
 * At TV Tropes (and by extension here), due to The Great Crash, certain examples and TV Tropes Made of Win Archive articles were Lost... Forever...
 * From That Guy With The Glasses:
 * A video by That Dude in the Suede that ranted against Youtube's takedowns of The Nostalgia Critic episodes which caught the interest of Doug Walker and in turn was responsible for That Guy With The Glasses/Channel Awesome becoming a showcase for more contributors other than Walker is lost and gone forever. The reason? Suede said he'd delete the video when the dispute between Walker and YouTube had run its course and Suede had saved the video on a now long-gone college computer.
 * Every single video that Daniel "That Aussie Guy" Rizzo made for the site.
 * The Nostalgia Chick's controversial review of the Dune movie.
 * In the same vein as the above, many a YouTube video has become Lost Forever due to the creator deleting their account, or, more often, the video being taken down due to copyright infringement.
 * Thankfully, this is becoming far less common with the increasing accessibility of software and browser plug-ins that allow fans to download videos. Any single video (or even a channel's entire video library) with even a modest amount of popularity will likely be downloaded by somebody somewhere along the way. And more often than not, when a popular channel ends up biting the dust, at least one fan will step up and repost one, some, or all of that dead channel's video library.
 * Several writers of the original Darwin's Soldiers RP on Furtopia played out scenes via private messaging. Those scenes were never released... not even to the GM.
 * Fanfiction.net never lets any Fan Fiction remain on the site forever. Which is sad, since the Wayback Machine can't archive anything there...
 * Public user photo site Fotopic went into administration in 2011, taking with it 8 years worth of images, websites, galleries... the lot. And with the Wayback Machine unable to save anything from it, it's all gone for good.
 * There is a wiki for this trope, but it's in it's early days and needs some Wiki Magic.

Real Life

 * The Honjo Masamune, probably the most famous sword made by the swordsmith Gorō Nyūdō Masamune, was by and large considered the single finest katana ever made and was a personal treasure of the Tokugawa Shogunate, as well as a Japanese National Treasure. In 1945, Prince Tokugawa Iemasa entrusted the Honjo Masamune and 14 other swords to a Police station in Mejiro, only for them to be given to a sergeant of the 7th Air Cavalry of the United States Military one month later. Since then, however, the whereabouts of the sword are completely unknown.
 * 'The Greatest Generation' really got their hands on a lot of cool loot.
 * There are 106 missing episodes of Doctor Who, destroyed to make room in the BBC archives.
 * And countless other lost TV series and episodes, as seen on Keep Circulating the Tapes.
 * Many films, especially from the silent cinema and early 'talkie' era, were not well archived, and as such they either vanished into the dustbin of history or had missing scenes.
 * And the earliest methods of copying the films for distribution actually degrades the strips that's being copied from.
 * In one of the ballsiest moves in the history of modern music (from a band that made their entire career on being ballsy), anti-establishment electronica duo The KLF celebrated their departure from the music industry by deleting their entire back catalogue. If you want to hear their music now, good luck finding old copies of their records on eBay.
 * To clarify, the term "deleted" means no longer in print by request of the artist. This happens a lot, but the artist usually only "deletes" an album/single or two, not their entire discography. It's pretty easy to find their discography on the internet, minus a few releases that may or may not exist. Whether or not the master tapes still exist is up for debate.
 * Any time a species goes extinct.