The Binding of Isaac

""There's something sinister about this title...""

- TotalBiscuit



The Binding of Isaac is a hybrid Roguelike/shooter made by Edmund McMillen, a co-creator of Meat Boy, and Florian Himsl, released in September 2011.

The story follows Isaac, a young boy who is in possibly the worst situation imaginable. After his mother heard commands from God that she followed without question, she is commanded to kill her son in sacrifice to prove her devotion. Isaac manages to escape into the basement, and is on the run as he fights off demons both physical and mental, discovers secrets about his mother's past, and ultimately confronts her in an effort to survive.

An expansion, Wrath of the Lamb, came out in May 28th of 2012. It adds a new category of collectibles called "trinkets," plus new and upgraded items, enemies, bosses, alternate areas, room types, a new character, a new ending and more. It has a trailer. Be afraid.

A character page is now under construction. Please contribute!


 * 1-Up: There is an item which gives an extra life without drawbacks.
 * 100% Completion: The "Golden God" achievement is obtained for getting all the items in the game.
 * The "Platinum God" achievement is a step further: You need to collect all items from the vanilla game and Wrath of the Lamb.
 * 20% More Awesome: The video announcement for the Halloween update states that the game is now '20% more evil'.
 * After Action Report: When you die, you get to see a will listing what killed you and which powerups you picked up.
 * All Just a Dream:
 * And Your Reward Is Clothes: Did you beat ? Congratulations, have a fez! ...What, you were expecting an ending?
 * Attack Drone: Some of the of the powerups.
 * Awesome but Impractical: The Brimstone item. It turns you into a black, horned demon and makes you fire bloody beams that not only deal significant damage, but also pierce enemies and obstacles, allowing you to quickly clear a room if the enemies are lined up. The price? It's only found in the Devil Room (costs about two hearts) or dropped by The Fallen (a rather difficult boss). And, unless you have one of a few specific powerups, like Chocolate Milk or a familiar, you can't attack until it's fully charged (which can take between two and five seconds). That said, if you've mastered the weapon's idiosyncrasies and can soak the health cost, Brimstone moves firmly into the Difficult but Awesome category.
 * A recent patch severely nerfed the Brimstone + Chocolate Milk combo. However, you can now begin charging a new Brimstone the moment you release the previous one -- that is, while the beam is still firing. This arguably pushes Brimstone into the Awesome Yet Practical category.
 * The Dr. Fetus powerup. Good luck trying to kill hosts with it.
 * From Wrath of the Lamb, the Mega Fetus powerup goes straight into Awesome Yet Practical territory, counting as mega-bombs (thus able to blow open doors, and dealing more damage) as well as being easier to aim. The Ipecac Syrup, also added in the expansion, is even MORE Awesome But Impractical- on the one hand, it can blow open doors AND poisons enemies, but on the other hand it travels in an arc that can make it very difficult to work with, especially on faster enemies.
 * Mom's knife; carries tremendous firepower but severely restricts your range and disables a great deal of potential powerups.
 * Several of the most powerful rechargeable items and consumables skirt Too Awesome to Use territory.
 * Several rare items, particularly in combination with each other, would be awesome but for the impractical, randomized nature of the game that keeps you from actually finding them.
 * Biblical Motifs: And a storyline, and a ton of references. Plus, The Bible itself appears as a collectable item.
 * Biting the Hand Humor: Inverted Trope (or played straight?) with the (incredibly useful if picked up early) Steam Sale item, which cuts-down all Shop prices by 50% (rounded down!)
 * Considering sales skyrocketed when the game was included in the Voxatron Humble Indie Bundle for charity....
 * Bloody Bowels of Hell: The game leans heavily towards this over Fire and Brimstone Hell.
 * Bloody Murder: Almost all enemies use weaponized blood to attack. With the correct upgrades, Isaac can too.
 * Boring but Practical: The battery allows you to charge up your item much faster than usual, if you stick around in combat for a while. Simply kill all but a single enemy, and dodge until you get all you can out of it.
 * Likewise, one item allows you to restore half a heart for every 13 enemies you kill. One regenerating enemy can regenerate back from the point after they count as a kill for the purpose of this item. Like the above, it's a slow slog to max health, but there's a good chance it's worth the trouble.
 * The same can be true when you're in the later levels and find an arcade. In fact, the more useful it is, the more boring it becomes.
 * Boss Rush: Many of the bosses will also make encore appearances as Degraded Bosses sometimes two at once. The challenge rooms become this in later levels.
 * Taken Up to Eleven with Wrath of the Lamb's "Curse of the Labrynth". This Random Event basically combines two floors, meaning you'll have to fight two bosses one after the other. There's also special challenge rooms that only spawn bosses, even at earlier levels (and they spawn harder bosses in later levels); these rooms are normally accessible only if the player has one or half a heart left.
 * Brutal Bonus Level:
 * And as of the Halloween update,
 * Now with the Wrath of the Lamb update,.
 * Bullet Hell: Things can get quite ugly with several shooting enemies on the screen.
 * The Cameo: One of the available powerups is a chunk of meat which, after collecting several, can be used to create a Meat Boy who will follow you and help fight enemies. There's an achievement for finishing him.
 * The walls of the Arcade are lined with posters of other McMillen games (like Time Fcuk).
 * Let's not forget the alternate versions of certain bosses.
 * Cast From Hit Points:
 * The Devil Rooms, which exchange Max HP (or Soul Hearts) for items. There are also several items that damage the player when used. The Halloween update introduces Eve, who runs on this and Critical Status Buff.
 * Wrath of the Lamb further builds upon this trope with spiked doors that lead to special red treasure chests, as well as sacrifice rooms and demonic beggars that reward the player for damaging himself.
 * Several items like the Dead Bird and Red Patch will only activate if Isaac takes damage.
 * Cartoon Bomb: With a skull (or sometimes a trollface) on it.
 * Charged Attack: The chocolate milk enables a Hold-type attack. Brimstone is also hold-type. However, having both allows Brimstone to fire without needing to charge... at least, it used to.
 * Confusion Fu: This is the basic niche of the Dead Sea Scrolls. It basically gives the effect of a random spacebar item per charge.
 * The 3 Dollar Bill give your tear a effect that change in every room you visit.
 * The new spider enemies from Wot L have quick and erratic movements. Their movements are impossible to read and thus are the bane of prospective No-Hit runs.
 * Crap Saccharine World: Cutesy Thick Line Animation, adorable characters.... and the horrific monsters they have to beat to avoid becoming a red smear on the basement floor.
 * Creepy Basement: Hoo, boy.
 * Cursed with Awesome: Various items, mostly found in the Devil Room, do this. In addition, certain Challenge Runs introduced with Wrath of the Lamb can actually be easier than a standard run.
 * Darker and Edgier: Compared to Meat Boy. And that's saying something.
 * Dead Baby Comedy: Powerups include a dead cat, the head of a dead dog or cat, a wire coat hanger which Isaac sticks through his head to make him cry more, and what appear to be two dead or possibly aborted siblings.
 * Considering the themes of the game, there's a good chance that the wire hanger through Isaac's head is meant to represent a homemade abortion tool...
 * Deal with the Devil: The Devil Rooms allow the player to exchange Max HP for items. Wrath of the Lamb introduces the demonic beggar, which damages the player in exchange for the possibility of dropping an item.
 * Death of a Thousand Cuts: Maxing out tears in the early floors can result in this depending on your base damage. Isaac with full tears and no damage upgrades can take down high level bosses such as Loki and Monstro II competently by swarming them with tears. Even more deadly with piercing, homing or curving tears.
 * The thin odd mushroom deliberately invokes this by increasing rate of fire to maximum while reducing damage.
 * Degraded Boss: Many bosses can reappear somewhere as a "normal" enemy.
 * Denial of Diagonal Attack: While it is possible to influence the angle of your tears by moving strategically, other than that you'll have to make do with just the basic cardinal directions. Whipping shots becomes impossible with Technology and Spoon Bender and similar items have no effect on it.
 * Desperation Attack: The Whore of Babylon item, which makes the player much stronger when having only half a heart. Eve starts the game with this item. It's not a Desperation Attack if picks up this item, as it is always active.
 * Wrath of the Lamb introduces a sort of desperation room, normally accessible only if the player has one heart remaining. These rooms always contain a special item...but they're also challenge rooms that spawn bosses when the item is taken. Again,  can always enter these rooms.
 * Difficult but Awesome:
 * allows you to shoot bombs instead of tears. On one hand, it can hurt you and it takes good timing. On the other hand, you have limitless bombs and enemies (especially bosses) die REALLY easily.
 * Taken Up to Eleven with the Ipecac Syrup in Wrath of the Lamb. Does more damage than bombs and poisons on hit, but its arcing path is very difficult to work with.
 * Eve also has shades of this with her One-Winged Angel form accessible with one of her starter items (see Fragile Speedster/Glass Cannon below for more details).
 * Distant Admiration fly. With proper skills, it can kill a boss relatively quickly.
 * Mom's Knife. Incredible attack power, terrible range unless you charge it (and there's no indicator of how much you've charged it, so that's basically guesswork).
 * Dungeon Bypass: The "We Need to Go Deeper" shovel allows you to dig down to the next dungeon level without finding and beating the boss (and, if you're not judicious about using it, without picking up the powerups you'll eventually need to win the game).
 * This can also be used to get to early.
 * Eleventh-Hour Superpower: Level 4 Meat Boy, who can only be obtained without bug-exploitation just before the start of the last level of the game. He will crush almost everything on that level with ease if you can stay out of the way for more than a few seconds.
 * Subverted in one of the Challenges added to Wrath of the Lamb, where you begin the game with a fully-upgraded Meat Boy.
 * Elite Mooks: Each enemy type has a tougher, tinted / colored version that will almost always drop an item when killed.
 * Different colors have different meanings, which are NOT consistent between enemies. An orange Knight won't act like Orange Chub.
 * Enemies with Death: You get to fight Death, one of the Riders.
 * Empty Room Until the Trap: Each level may have one specially marked room with a chest or item that, if you open/take it, will trigger three waves of enemies.
 * Everything Trying to Kill You
 * Evolving Weapon: The Cube of Meat, an item that only drops from The Harbinger bosses. Every cube you get increases how effective the powerup is. It also reminds one of a certain skinless boy after the second cube.
 * Exploding Barrels: Wooden barrel variety.
 * Fan Nickname: Meatboy Lvl. 5 - That's the way some players call the severed body "generated" by The Shears. The reason behind it is because it used to be possible to have constantly following you by acquiring five Meat Cubes via glitch exploitation.
 * Until they are revealed, the new Wrath of the Lamb enemies.
 * Gainax Ending: All the endings except the first, "Epilogue". The general format is: Isaac beats Mom, goes for two more levels, and kills, which drops a giant chest. Isaac opens this chest and finds an item which will be available next game, which he is unduly excited about, and optionally something bad happens to him. Especially notable for Mind Screw is the "Everything's Terrible!" ending, where  No resolution of the plot from the introduction actually occurs. For that matter, the intro plot and normal ending combined make up a story that doesn't really fit with the rest of the game.
 * The "final" ending from the update turns this Up to Eleven.
 * Exploding Barrels: Wooden barrel variety.
 * Fan Nickname: Meatboy Lvl. 5 - That's the way some players call the severed body "generated" by The Shears. The reason behind it is because it used to be possible to have constantly following you by acquiring five Meat Cubes via glitch exploitation.
 * Until they are revealed, the new Wrath of the Lamb enemies.
 * Gainax Ending: All the endings except the first, "Epilogue". The general format is: Isaac beats Mom, goes for two more levels, and kills, which drops a giant chest. Isaac opens this chest and finds an item which will be available next game, which he is unduly excited about, and optionally something bad happens to him. Especially notable for Mind Screw is the "Everything's Terrible!" ending, where  No resolution of the plot from the introduction actually occurs. For that matter, the intro plot and normal ending combined make up a story that doesn't really fit with the rest of the game.
 * The "final" ending from the update turns this Up to Eleven.


 * Game Breaking Bug: One of the new items introduced in the Halloween update, Brimstone, causes Isaac to shoot enormous streams of blood from his mouth. Sounds awesome? Depending on which upgrades you get or currently have, you may end up being unable to attack at all. The boss of the level added at the same time as Brimstone was also initially immune to it due to a bug.
 * Another glitch from Halloween update: The Headless Horseman would sometimes replace the boss of the new level. This wouldn't crash the game, but this would horribly distort the music
 * A similar glitch to the above used to happen in Wrath of the Lamb. The Random Event "Curse of the Labyrinth" combines two floors from the same tier into an "XL" version, causing the player to have to fight two bosses, one after the other. It is possible for the Final Boss to be the first boss fought in the Depths XL (or it's alternate, the  XL). Normally, when the Final Boss is defeated it becomes impossible to leave the room, and if the boss is fought first in the XL version then the game would not recognize the level has been completed. This left the player stuck in an inescapable room, unless he can use a teleportation item. A similar thing could happen with  . Thankfully, this bug was fixed a few days later.
 * Not exactly game breaking, but there's the whole mess with Wrath of the Lamb's  The boss screen shows   Previously it was  . Currently it's  . This created a lot of Epileptic Trees.
 * God Is Good:
 * Gorn: Most of the bosses and enemies are quite disgusting, along with several powerups.
 * Grossout Game
 * Guilt Based Gaming: If you try to quit the game, Isaac will ask you "Are you sure you want me to die?"
 * Heart Container: These can be found here and there, although only one of them resembles a heart. Some even grant two Max HP, and/or restore all your health when you get them.
 * It does so in the literal anatomical sense, although it is named <3.
 * Wrath of the Lamb adds Eternal Hearts. Get two, or complete the level with one, to add one Max HP.
 * Hoist by His Own Petard: Those shot-blocking, sheild-like orbiting flies can be pretty annoying when it's your shots that are getting blocked by them. Some enemies have invincible "Holy" flies that shots cannot penetrate.
 * Inexplicable Treasure Chests: Treasure chests are everywhere in the basement of the house. Even more inexplicably in
 * It's possible to unlock a treasure chest and find another smaller treasure chest inside, and (although very rare) it's possible that chest has another still smaller chest inside it!
 * Infinity+1 Sword: Isaac's secret starting item. You need to beat the game's true final level ten times, which is quite a lengthy and dangerous task. And after that, you need to beat it once again with the resident Joke Character! An extremely painful ordeal! But if you manage to accomplish this mission, your reward will be...
 * Another one shows up in the Halloween Update.
 * Incredibly Lame Pun: "What a WHORRIBLE night for a curse!"
 * Interchangeable Antimatter Keys: In classic Zelda style, any key fits all locks, but disappears once used.
 * Invincibility Power-Up: The My Little Unicorn and the Gamekid powerup. To a lesser extent the Book of Shadows.
 * Ironic Nursery Tune: Heard in the credits after the very last ending, received from beating the game ten times.
 * It Got Worse: One of the rewards is making the game more difficult after beating it a certain number of times.
 * Jack of All Stats: Isaac starts as this.
 * Master of None: Before you unlock his item. See Magikarp Power and Infinity+1 Sword.
 * Joke Character:, unlocked by beating the true form of the game's True Final Boss (you read that right), and who you need to beat it again with to unlock yet another item. He starts with the same stats as Isaac (not even Cain or Judas's improved offensive stats) except all his hearts are soul hearts -- and for the entire game, all health upgrades he collects are instead soul hearts, meaning he can never have any health except soul hearts. He does start with an item though! Why yes, play as and you can start the game with...
 * Joke Item: The Poop, which just drops a pile of dung where you're standing and can be used once per room. Maybe it can be used for cover and maybe it can be used to block an enemy chasing you, but virtually any other item is more useful in any situation.
 * It's only good in areas with small passages. Note that shooting poop sometimes spawns a pickup.
 * King Mook: Chub.
 * The Krampus: Added as a boss in the Christmas update. The Krampus will randomly appear in the Devil room with the chances of him increasing the more you visit the room and even more if you actually take items.
 * Last Ditch Move: Some enemies explode, while some others spawn bullets when killed. For bosses, Steven has a last-ditch move.
 * Due to a glitch, sometimes the effect of final bosses dying can actually hurt you.
 * The Legions of Hell
 * Lethal Joke Character: . His health is entirely made up of hard to collect Soul Hearts, and he begins with the least useful starting item of all the characters. However there are a couple of quirks that can increase his power throughout the playthrough quicker and far beyond the other characters. First, he is able to enter Challenge Rooms (and Wrath Of The Lamb boss challenge rooms) at any time. Second,.
 * Additionally, all items that activate at only 1/2 heart are always active for him, such as with the tried and true Whore of Babylon. The Wrath Of The Lamb DLC brought a number of these to the table, increasing the exploit potential. For example, having the Polaroid now means that always has increased Mercy Invincibility.
 * Lethal Joke Item: The takes forever to recharge and doesn't even deal damage, but kills the final boss and the True Final Boss in one use. Don't try to use it on the Bonus Boss, though. Just don't.
 * By extension, the has a fairly disappointing obvious effect, but it can often be used to cheat the devil out of some of his nicer items without dying and has the side effect of making a  more likely in shops, guaranteeing an easy final boss if you get it.
 * The Book of Revelations has an appreciable effect, but is likely to be passed over for a more dramatic (and faster charging) item. The Book of Revelations plus the Battery plus patience, however, means one free soul heart per room for the rest of the game. Play conservatively and it's almost impossible to lose. A few other items can be similarly abused.
 * Also, the Book of Revelations makes it much more likely that you'll fight a Harbinger in the boss room, letting you quickly build up your Meat Boy familiar.
 * Wrath of the Lamb introduces the Prayer Card, which is the Book of Revelations on steroids. Instead of soul hearts, it gives eternal hearts, a new heart type introduced in the expansion. What do eternal hearts do? They're similar to soul hearts, except you can only have one-half of an eternal heart at a time... because if you get two halves of an eternal heart, or complete a level with half an eternal heart, it becomes a new Heart Container. Prayer Card and the Battery can let you break the game wide open.
 * Another WOTL blatant game buster is the Nun's Habit. It charges up your current item by 50% when you suffer damage, giving you a new use every two hits received. Sounds nice and all, but then you pick Maggy's Yum Heart, which restores a whole heart, or the Book of Revelations, and you become virtually inmortal all the way to the, since most hits drain a half of a heart. Add the Wafer item on top of that, which reduces all damage to 1/2 heart, and you have legitimately enabled godmode.
 * Let's Play: A few on Youtube. One notable example is Northernlion. Here's the first episode. Watch as he goes from complete newbie to expert over the course of 90+ videos!
 * This ultimately culminates in an episode with co-commentary by Edmund McMillen
 * Living Apart: In later levels, brain enemies are encountered that are just living brains. There are also rolling guts in the later levels.
 * Losing Your Head:
 * Some of the enemies can attack the player even after losing their body or head or they just get separated.
 * Transcendence removes the player's body, allowing you to float over rocks, pits, spikes, and damaging liquids. One of the better items.
 * The Shears and the "The Hanged Man" Tarot card also do this, but only for one room. Also if Isaac has items that make him look demonic he gets wings instead.
 * Luck-Based Mission: The items are not all equally useful, and other than a guarantee of one major item and one shop per level (possibly both behind locked doors you can't open, and the shop could have anything from two hearts to four major items or be replaced by a boss who drops nothing of value) plus a major item dropped by each boss, how many items you get is somewhat random. The pill item is explicitly random in the fashion of Roguelike potions (though it has more positive than negative effects), after-battle rewards are random, and not all bosses are equally hard. Finding an arcade can often mean an end to needing to pay attention to your supply of bombs, keys and/or money for the rest of the game and can also grant some pills and fly shields -- but it's also completely random whether you'll even find one, and getting any items from the games within is also luck-based. Basically, there is always a chance that you will reach the end of the game with a much more or less powered up character than you expected through no fault of your own. On the extreme, it's possible to get absolutely no useful upgrades, all bonuses being activated items that you do not want, or things your character doesn't benefit from at all; on the other side it's possible to get a few bonuses that work well with each other and a lot of arcades along the way, getting to the last level with maximised stats, shots that pass through walls, and twelve hearts.
 * Acquiring 4 Cubes of Meat! It requires you to fight and kill all four Harbingers in a single playthrough... Unfortunately, there's no guarantee you'll encounter all of them in a single run, even after acquiring a Book of Revelations, (another luck mission on itself) which supposedly guarantees you to fight all of them.
 * Doing the no-damage runs is also highly luck-based. Get a room full of five leapers of a long trek to the boss room? You can forget about getting the achievement that run.
 * The Random Number God may drop that room several times in a row.
 * Not to mention the addition of the Alternate Floors in Wrath of the Lamb, which replaces half the enemies with more difficult counterparts!
 * Bosses also constitute to the luck-based nature of the game. Not all of them are equally difficult, and depending on a character you choose and powerups you get, some might be a cake-walk (Larry Jr., Loki, etc.) and some an endless source of frustration (Gurdy for a slow-moving character, Monstro II for people who dislike close-range combat). And since not getting hit (which is more difficult if you get a boss you are faring poorly against) is almost a requirement for getting access to the devil room, which often allows one to balance the odds, the difficulty snowballs depending on how much Random Number God loves you.
 * Luck Stat:
 * The original game had an item called the Lucky Foot that increases luck - which in this case means better pills, rewards from locked treasure chests, and better chances of Rewarding Vandalism and winning the skull game.
 * Wrath of the Lamb introduces items that explicitly increase or decrease luck. It's unclear if this is related to the Lucky Foot or not.
 * Ludicrous Gibs: The fate of every single enemy you destroy is being turned into these.
 * Lying Creator: "BIG HALLOWEEN UPDATE (with no actual lame Halloween themes)".
 * Macrogame: Each playthrough is different than the previous one, but as achievements are unlocked more and better items begin appearing.
 * Magikarp Power: After you start unlocking the secret characters, Isaac becomes a lot less useful, because the other characters' starting items grant them a great edge over him despite their specialized stats. HOWEVER, if you manage to unlock his own starting equipment, he suddenly becomes game's most powerful character!
 * Memento MacGuffin: The Polaroid trinket, which depicts Isaac's family before the madness started. Getting knocked to half a heart with it on gives Isaac a protective shield.
 * Mighty Glacier/Stone Wall: Magdalene starts off as this.
 * Mood Dissonance: The Arcade rooms are very nicely furnished and bright, with a very chipper 8 bit remix of the first level theme. It's a bizarre contrast to the rest of the game.
 * Mook Maker: Several of the bosses, though not all of them. Also one of the enemy types.
 * is a Degraded Boss Maker.
 * Money for Nothing: Once you reach, money has very little use.
 * At least until you get your hands on a Money = Power
 * Mythology Gag: Several of the bosses and items are references to other works by Edmund. Namely, the Cubes of Meat, Dr. Fetus and Mega Fetus, the Super Bandage, Larry Jr., C.H.A.D., Steven and Li'l Steven, blobs that look like Gish, Gish himself as a boss and possibly  in Wrath of the Lamb.
 * Multiple Endings
 * Mundane Made Awesome: After everything that just happened, Isaac gets rather surprisingly excited over the items in the endgame chest, including.
 * Nintendo Hard: No continues. You start with one life, and no guarantee of additional lives being available. If you die, you start all over again. The configurations of rooms and upgrades are randomized and in some situations damage will be unavoidable. Survival depends on reflexes and calculated risk.
 * And Wrath of the Lamb takes this even further! If you thought the vanilla version was merciless, you won't survive the new horrors you'll face here! Good thing you also get new (and Awesome Yet Practical!) power-ups to help you compensate the difficulty boost.
 * No Cutscene Inventory Inertia: No matter what the player has picked up, the character at the cutscenes is still what he was at the beginning.
 * For that matter, it'll still be Isaac no matter which character you're playing as.
 * No Damage Run: A no damage run of each area will earn you a Steam Achievement. It's also enforced with at least two characters in different ways.
 * No Ontological Inertia: Averted, any flunkies spawned by a boss will not die when the boss does (except in the case of Mom) and must be killed in order to clear the boss room.
 * Obvious Beta: Let's be honest: the expansion is as glitchy as hell. Even the patches can create further bugs; version 1.15 prevented several players from unlocking Challenge 10 or Ending 12.
 * Offing the Offspring: Unsurprisingly, since the game was named after the original, the Choice of Abraham kind.
 * Old Media Are Evil: The plot and imagery are inspired from inflammatory Christian propaganda from The Eighties, such as the Jack Chick comics.
 * Ominous Latin Chanting: In "Enmity of the Dark Lord", the song that plays when you fight.
 * One-Winged Angel: For an example not involving, see the Eve entry under Fragile Speedster/Glass Cannon.
 * Palette Swap: Enemies with a different color palette. They're stronger but drop items upon death.
 * Paper-Thin Disguise: It's heavily implied that the unlockable characters are just Isaac wearing these.
 * Potty Failure: The item "Lemon Mishap" allows you to lay down a puddle of pee that damages. Also, certain pills will give you bad gas or literally explosive diarrhea. There's also the boss monster Peep, who uses urine as his main weapon.
 * Critical Annoyance: Isaac leaves puddles of urine every room he enters when he is down to his last hit point.
 * Purposefully Overpowered: The Wrath of the Lamb expansion adds a lot of incredibly powerful new items and effects that would be extremely abusive on the vanilla version of the game; you'll need every one of them if you want chance to survive (not win, just survive!) the horrors you'll find on the new floors.
 * Power-Up Letdown:
 * The cat item. You have eight extra lives, yes. You also have your health bar reduced to one heart (and any health bar increases you find vanish on respawn), and if you die you respawn outside (with your secondary item still used up if you used it and any Faith Hearts still gone) and enemies fully heal. So good luck beating any bosses you couldn't kill on the first try. And those eight extra lives are going to need to last you the entire rest of the game.
 * Also the mirror, which turns all your shots into boomerangs that follow you. These have abysmal range (and any range pickups you get make them boomerang further, which is pretty much useless) and behave in goofy ways which can be hard to predict or keep track of because they follow you rather than a trajectory. They could theoretically be useful but you'll probably just get hit more by having to think about them.
 * A high speed stat, as well. You'd think it'd be useful, but once you get four or five it becomes very difficult to control the character and prevent yourself from careening into spikes, monsters, fires, shots, etc. Less obvious/problematic with flight.
 * In a crossover with Cursed with Awesome is the Bad Trip pill. If you use it with the usual health bar (as you likely are, testing pills), you suffer 1 heart's worth of damage - but if used while at exactly one remaining heart of health, it acts as a Full Health pill.
 * Samson, a character added in Wrath of the Lamb, is basically ... but with a lower base attack. (He is skilled at fighting mobs of enemies, but that's not much consolation if you have to fight one of the few bosses that doesn't summon punching bags.)
 * Ipecac, which replaces your tears with a lobbed green poison bomb similar to Sloth and Pestilence. It has a lobbed trajectory making it hard to determine if it will hit rocks or not, can damage you with its explosion and makes it ridiculously hard to fight flies and quick running enemies that chase you around. If this is your first treasure room pickup as Judas, your game could end in less than a minute.
 * Power-Up Magnet: There's a Magneto powerup which attracts powerups even through rocks and over gaps.
 * The Power of Love:, a picture of , shields Isaac on his last hit point and instantly kills Mom and upon being brought to the battle. Originally, it defeated  too, but this may have been a bug.
 * Psychopathic Manchild: Several bosses give this impression due to the goofy, yet deranged smiles they make when attacking.
 * Random Event: The Curses introduced in Wrath of the Lamb, which are randomly activated at the beginning of a level. Curse of Darkness makes the map useless, while Curse of the Lost increases the size of a floor from what it would normally be. Curse of the Labyrinth combines two floors of the same tier - including two item rooms and two bosses.
 * Refuge in Audacity
 * Reset Button: Forget Me Now, an item unlocked by . It starts you over from the beginning of the current level with a new layout and new monsters, including the boss. Why would you want to use this? The reset level also has new items, giving you more opportunities to power up your character. The only problem is that Forget Me Now is a one time use spacebar item, forcing you to abandon your current spacebar item and beginning the reset level with that item slot empty.
 * Revive Kills Zombie:, while normally dealing no damage, kills Mom instantly.
 * may also do this.
 * Rewarding Vandalism: Occasionally, destroying poop and putting out fires drops an item. Rocks with a small X on them (usually identifiable by their color) will also drop an item when bombed. And then there's the secret rooms, which are revealed by blowing up walls.
 * Roguelike: Things like level layouts, monsters, items and most bosses are randomly generated - though it's also level dependent (i.e. you will never a Caves boss in the Basement, unless the boss could appear in both). Wrath of the Lamb even randomizes what level you'll be sent to by providing alternate stages. For example, in the original version the first two levels would always be the Basement. After the expansion, each of the first two levels will be either the Basement or the Cellar.
 * Scare Chord: Played on certain endings and when you enter the Devil Room.
 * Secret Character:.
 * Sequential Bosses: Particularly
 * Seven Deadly Sins: Personifications of these are present in this game as minibosses. Beating all seven unlocks a new item. Super versions appear in Wrath of the Lamb.
 * Smart Bomb: The death tarot card, Necronomicon, and one of the functions of the Sun tarot card.
 * Shout-Out: So, so many.
 * The 1-up mushroom that follows you around is green with white spots.
 * There's also the Magic Mushroom and the Mini Mush, which are direct references to Mario's Super Mushroom and Mini Mushroom
 * The Bobby-Bomb walking bomb upgrade is a clear reference to Bob-Omb.
 * The HUD and basic rooms are very blatant ones to The Legend of Zelda.
 * Some enemies are also reminiscent of Zelda enemies. The most noticeable are the Chargers (which behave like Ropes) and Knights (which behave like Darknuts).
 * Teleportation items may randomly send you to a room with a guy saying "I AM ERROR"
 * Wrath of the Lamb's candle is pulled straight from Legend of Zelda.
 * The Wrath boss is basically Bomberman.
 * One weapon upgrade is Sad Onion.
 * Another is Steven, A tiny head that grows out of your skull. He also appears as a boss.
 * Chub's weakness is eating a bomb.
 * A number of internet meme faces make an appearance, particularly the Forever Alone and Troll faces, with the latter appearing on bombs which are ready to go off. And let's not forget Shoop-Da-Woop!, which charges ya laser.
 * There is also an enemy type with a distinctive Trollface that will split in half upon gaining enough damage, and the duplicates will split further into even smaller copies, demonstrating the spirit, as well as appearance of the Trollface. In its smallest form it becomes a Pokerface.
 * One enemy type is the same species as Gish.
 * "Pills Here!" message after picking up a pill is a shout out to Left 4 Dead.
 * One effect that pills can give you is "Balls Of Steel", which gives you 2 soul hearts.
 * The "My Little Unicorn" item seems to be a shout out to Robot Unicorn Attack and My Little Pony.
 * The "Technology" upgrade is a clear reference to the Borg.
 * Some boss variants are actually characters from other games. For instance, Chub the grub can sometimes turn out as C.H.A.D. the blood clot.
 * That fly that buzzes around your head to intercept bullets is Pretty Fly (for a White Guy).
 * A Shovel item that lets you skip a floor has the description "We Need To Go Deeper".
 * The Parasite power-up resembles the Parasite from the Flash-Game "The Visitor" from fellow Newgrounds contributor Zeebarf.
 * When going into the One-Winged Angel form accessible through one of Eve's starting items, the transformation is denoted by the phrase "what a horrible night to have a curse".
 * The Wire Hanger item is a reference to the film Mommie Dearest, in which an abusive mother screeches the famous quote: "No more wire hangers ever!"
 * One of Death's attacks is scattering spinning sickles all over the room, which fly towards the player.
 * Larry Jr. is a Human Centipede. It makes the pooping that much more disturbing.
 * He's also a callback to Super Meat Boy.
 * During one of the endings  There's also a power-up called "Doctor's Remote", which is another reference to the character in question.
 * One of the new items in Wrath of the Lamb is the Notched Axe, a pickaxe that can be used to break rocks. This could be a reference to the Notched Pickaxe from The Elder Scrolls V: Skyrim, which was itself a reference to Notch, the creator of Minecraft.
 * The Chemical Peel item will give you a Harvey Dent makeover.
 * An item named "Telepathy for Dummies", looking exactly like any "for Dummies" book would look like.
 * One of the power ups you can get from the Devil Room is called "Lord of the Pit", probably a reference to Magic: The Gathering.
 * Wrath of the Lamb adds "Spirit of the Night".
 * Skeleton Key: Gives 99 regular keys, which is probably all you'll need and then some. A straighter example appears in Wrath of the Lamb with the Golden Key, which allows you to open any door in the floor where you get it without spending any of you Interchangeable Antimatter Keys, then vanishes after the floor is exited.
 * Sorting Algorithm of Weapon Effectiveness: For the most part items unlocked later aren't any more powerful than those at the beginning... except the familiars, where the ones available at the start fire vanilla bullets and those acquired later have much more exotic and useful attacks. And the health-increasing items, where the unlockable ones generally either heal you or give you some soul hearts as a bonus.
 * Spikes of Doom: These appear in later levels in some of the rooms.
 * Sequence Breaking: It's possible to reach without beating the game ten times either by using the "We Need To Go Deeper" item or taking the hatch in the (possible) Devil Room in the supposedly last stage.
 * Sleeper Hit: Word of God has stated he never expected Isaac to be so popular.
 * Standard Status Effects: Paralysis, slowdown, poison. Interesting case since only Isaac gets to inflict them on enemies (with the exception of the Death boss).
 * Stuck Items: Your reusable item can only be replaced with a different one, though depending on the character you might start out empty handed. Likewise, you can only drop a one time use item by picking up a different one, which can be stressful if you end up holding one you know would be detrimental to your health if you accidentally used it.
 * Wrath of the Lamb adds trinkets, which can only be exchanged if you find another one. Trinkets are passive abilities, so this usually isn't a problem - but there is actually one trinket that cannot be removed no matter what. This is not a bug, although it is a literal bug; the trinket in question is a Tick. Ticks are hard to remove!
 * Surreal Horror
 * Tactical Suicide Boss: A few.
 * Loki drops Boom Flies that, if your offensive capabilities are strong enough, you'll immediately detonate on top of Loki.
 * A canny player can push Wrath's bombs back at him, dealing significant damage. If you've got the Homing Bombs powerup, you won't even need to do that.
 * One of the new bosses in Wrath of the Lamb, Pin, can actually damage itself with it's green exploding projectiles.
 * It's possible to have  step on another part of , dealing a large amount of damage.
 * Take That: A big one against conservative Christianity, and its television and print propaganda.
 * Judas wears a fez because Phil Fish, the creator of Fez, voted against Edmund McMillen in the Independent Games Festival, which Edmund felt was traitorous.
 * Take Your Time: Uniquely for a Roguelike, there is no time limit of any kind, and you can backtrack as much as you want within a floor.
 * Teleporting Keycard Squad: Taking an item or opening a chest in mob rooms triggers three waves of enemies.
 * Toilet Humor
 * Too Awesome to Use: Some of the Tarot cards and the Full Health pill, usable only once. Possibly some of the more powerful subweapons which can only be used once every six rooms.
 * Turns Red: All four of the Harbingers, Gemini, Peep to a minor extent, and . Some are actually less difficult after turning red.
 * Treasure Is Bigger in Fiction: Coins in this game are large.
 * True Final Boss:
 * Underground Monkey: In both new model and palette swap flavor. Even a few bosses come in variants, some of which being Shout Outs to other games.
 * Unstable Equilibrium: The end game is either too easy or nigh impossible depending on the items gathered. Some work wonders when complemented by other items, and other times you might as well not bother. Those items usually randomly given to the player instead of chosen, though. The D6 gives some leeway by re-randomizing items.
 * Unwinnable By Mistake: Thanks to a teleportation item (either pills or the Teleport! item) and some rotten luck, a player can find themselves stuck behind a room full of rocks, with no bombs to break them, making it impossible to continue, and forcing them to quit out of their current run.
 * It happened to the game author himself. In his co-commentary with Northernlion, he mentions that, after getting a certain combination of power-ups and power-downs, his firing range was too low to reach some monsters standing behind a pit -- and killing all enemies is required to leave a room.
 * The Wrath Of The Lamb expansion has issues with this, with XL levels being the main culprit. The player may teleport into an area with no exits, or the game may not spawn the hatch to the next level if certain bosses are fought first in the Sequential Boss fight.
 * The Very Definitely Final Dungeon:
 * Womb Level
 * A Worldwide Punomenon: Everything. Everything.
 * What Do You Mean It's Not Heinous?: Between levels, Isaac is shown curled in a fetal position having bad dreams, usually with people laughing at him. These dreams range from dying from the fall from one of the level-end trap doors to being given a pile of shit as a birthday present to discovering that there is no toilet paper left.
 * World of Symbolism: Downplayed. A lot of the stuff is just creepy, but when you start viewing it through the eyes of an abused child... The choice of the item powerups being definitely creepy:
 * HP ups being mostly spoiled milk and dog food, implying what Isaac is usually fed. "Nutritious" foods which give Isaac two hearts of max health include raw liver and buckets of lard.
 * Items used to beat/punish Isaac increasing his speed (wooden spoon, belt)
 * His pets all dead, presumably killed by Mom. (Tammy's head, Max's head, Eve's dead bird)
 * The Virus you often receive for beating Lust is AIDS/HIV.
 * The Brother Bobby, Sister Maggy, and wire coat hanger items, implying that Isaac is a failed abortion (unlike his siblings) and an unwanted child. (But isn't abortion against Christian beliefs?)
 * They could be
 * The other characters being alter-egos of Isaac -- he is so lonely he has to make them up in the first place.
 * The Wiki Rule: Natch.
 * X Meets Y: The Legend of Zelda meets Super Meat Boy meets The Bible... In Roguelike style!
 * Alternatively, The Legend of Zelda meets Diablo meets Invader Zim.
 * The Virus you often receive for beating Lust is AIDS/HIV.
 * The Brother Bobby, Sister Maggy, and wire coat hanger items, implying that Isaac is a failed abortion (unlike his siblings) and an unwanted child. (But isn't abortion against Christian beliefs?)
 * They could be
 * The other characters being alter-egos of Isaac -- he is so lonely he has to make them up in the first place.
 * The Wiki Rule: Natch.
 * X Meets Y: The Legend of Zelda meets Super Meat Boy meets The Bible... In Roguelike style!
 * Alternatively, The Legend of Zelda meets Diablo meets Invader Zim.