NetHack

""While the graphics may seem primitive by today's standards, today's gameplay seems primitive by Nethack standards.""

- Christopher Wellons

NetHack is old. The first version came out in 1987 and its development is still not finished. NetHack is complex. It can take years of play to see it all. NetHack is random. It is one of the three founding roguelikes and will sometimes generate levels that seem flatly impossible. But they never are.

NetHack has been described as a puzzle game hiding inside a roguelike's skin. Whereas the archetypal Angband or Dungeon Crawl hero is a knight in shining armour who slays countless evil creatures and becomes powerful like unto God, the archetypal NetHack hero is a cunning trickster (or... hacker) who sets traps, fights in unconventional ways and never, ever plays fair. After the very first few levels, killing monsters for XP becomes unprofitable (or even disadvantageous). Instead, power comes from your ever expanding collection of items which can be wielded, worn, thrown, rubbed, dipped, engraved, snapped, pointed, combined, cast, eaten, or applied, singly or in combination.

The advantage of NetHack's focus on items is that it reduces the impact of luck. By carefully hoarding your resources, (almost) nothing is inescapably fatal. The downside of NetHack's focus on items is that it reduces the impact of luck. Once you've learned some effective tactics, multiple playthroughs can start to feel similar, or even repetitive.

Still, for a free game (in the sense of both "free speech" and "free beer") that can take up to a decade to beat for the first time, you could do worse.

NetHack is cross-platform; it's safe to bet that if you're using an operating system that's still being developed, there's a port for it. In fact, Linux distributions tend to feature ports of it in their software repositories, and anyone with the proper programming skills can make ports or modifications because it is free and open-source software, released under the terms of the NetHack General Public License.

You can play it online here.

If Nethack's rather archaic graphics intimidate you, you can always try Vulture, an isometric GUI that more or less takes the original and spits out detailed graphics, sounds, and all around allows for an easier experience when learning how to play. The site currently has builds for vanilla Nethack, SLASH'EM and UnNethack, with the Sporkhack variant coming soon. Additionally, the Nethack Wiki has a list of other alternate graphical tilesets.

The voice of [your God] booms out: "Congratulations, mortal!"--More-- "In return for thy service, I grant thee the gift of Immortality!"--More-- You ascend to the status of Demigod[dess]...--More-- Do you want your possessions identified? [ynq] _]]
 * Acronym and Abbreviation Overload: The IRC channel for Nethack often combines this with the in-game symbols used to represent the various items; so a late game ascension kit might contain (among other things) [oMR, "oLS, a cursed !oGL and plenty of /oD.
 * Acquired Poison Immunity: and many other types of immunities besides.
 * Adam Smith Hates Your Guts: Can become this if you're hungry, have really low charisma, or are wearing a Hawaiian shirt.
 * A God Is You: For those, and also for the occasional attentive player who discovers that.
 * The latter is only unambiguously spelled out in the game's source code, but it's alluded to in a couple of other ways in the endgame sequence:
 * If you try tinning any of the corpses you get this message:
 * Of course, the real Four Horsemen are Conquest, War, Famine, and Death...
 * All Animals Are Dogs: The only way to tame most monsters is with a scroll of taming (or in some cases by wishing for a figurine), but throwing food (especially treats) to an already-tamed monster will increase their tameness, regardless of what kind of animal it is (as long as it's food they'll eat).
 * All Cavemen Were Neanderthals
 * All There in the Manual: The in game guide is a remarkable collection of quotes and information, not all of which is entirely accurate in describing game mechanics.
 * Amplifier Artifact: The Magic Mirror of Merlin gives Knights (and Knights alone) double damage to most of their spells.
 * Anachronism Stew: Let's see... playable characters include an Indiana Jones-inspired Adventurer Archaeologist, a Conan the Barbarian-style Barbarian Hero, a caveman, a Samurai, and a Hawaiian-Shirted Tourist complete with a credit card (used to pick locks). Items and enemies include traditional staples like Dragons, Demons and Giants, but also included are things like Grid Bugs, Quantum Mechanics, and Jabberwocks. Finally, plastic, while fairly uncommon, isn't unknown either.
 * Ascend to a Higher Plane of Existence:
 * Anyone Can Die: Namely, you.
 * Auto Revive: The.
 * Unless And it doesn't do much to remove the source of the death, either...
 * Bare-Fisted Monk: Despite not being able to effectively use weapons, monk characters can become extremely powerful and deadly.
 * Blindfolded Vision: Possible with Telepathy, and invoked by Intrinsic Telepathy.
 * Blinding Camera Flash: Tourists can use this as a weapon.
 * Block Puzzle: Sokoban, a four-level puzzle in which you push boulders to plug holes in the floor. The game mechanics change somewhat, though: You can't push the boulders diagonally or fly over the holes in the floor, and destroying the boulders (or creating more) nets you a Luck penalty.
 * Bolt of Divine Retribution: Tick off your god enough, and you'll get struck by lightning.
 * If you manage to
 * Bottomless Bladder: The PC isn't required to sleep and recovers from wounds without having to rest. In fact, the only source of restful sleep is delivered by an amulet of restful sleep, which can be used to heal, but is mostly just there as a hazard.
 * Averted with SLASH'EM. There are toilets, but their use isn't obvious at first. If you're Satiated and sit on one, you "take a dump" and lose some nutrition, along with being cured of sickness. It is extremely likely someone will never use it anyway, but it's there.
 * Breakable Weapons: A variant: you cannot break melee weapons through fighting with them, but using bladed weapons to force locks can break them. Missile weapons have a chance of being "lost" (i.e., disappearing from the game) when they are used.
 * Breaking the Fourth Wall - Applying a stethoscope to listen to the very bottom of the screen gives, "You hear a faint typing noise."
 * Cap: Several things are capped in Nethack.
 * The player's ability scores are capped at 25 (after all bonuses are applied).
 * The highest possible Luck score is 14 (13 if it isn't a full moon).
 * The player's experience level is capped at 30.
 * Monster hit dice (for "normal" monsters) are capped at 49.
 * There are quite a few things that aren't directly capped, allowing them to go as high as 2^8-1, 2^16-1, 2^31-1, or possibly even 2^63-1 depending on the size of the variable they're stored in.
 * Cherry Tapping: Typically "Vladsbane", named for one boss so wimpy he can be dispatched with a rusted tin opener or thrown magic marker.
 * Chest Monster: Mimics lurking in stores are common killers of low-level characters.
 * Color Coded for Your Convenience: Unicorns are color-coded by alignment: black/chaotic, grey/neutral, white/lawful. Many other monsters, particularly dragons, are coded by properties: monsters with fire attacks (pyrolisks, hell hounds, red dragons) are usually red, monsters with cold attacks (blue jellies, winter wolves, white dragons) are usually blue or white, etc.
 * Combinatorial Explosion: Sometimes literally. But no matter how funny it would be, never ever . For that matter, don't either.
 * Commonplace Rare: Two of the most useful items in the game are: a magic marker and a can of grease. Both are disgustingly uncommon. Grease is mostly valuable because it is rare--its effects are important but mostly supersedable (armor can be made permanently damageproof and there's a cloak and a bag that are effectively permanently greased. You'll still have to avoid melee with mind flayers). Magic markers, however, let you write powerful and valuable magic scrolls on junk parchment (and are used up in the process), making them quite desirable.
 * Another inexplicably uncommon item: shirts. T-shirts and Hawaiian shirts have no armor value in and of themselves, but can be enchanted to give a valuable extra few points of protection. If you can find one. Wishing or polymorphing may be necessary.
 * Convection, Schmonvection: Mostly averted. You can stand next to lava with no ill effects but if you try even flying over it without fire resistance you're in for a world of pain. Water Walking boots will let you walk over lava, but if they aren't fireproof themselves the lava will destroy them, then you fall in and die as a result.
 * Crazy Prepared: The player, if they intend on being successful.
 * Critical Existence Failure: Down to one HP? Go ahead and kick a wall. I dare you.
 * Damage Discrimination: Averted; if you're facing a mob of enemies, anyone between your character and a missile-user (up to and including dragons) stands a chance of getting hit. Also, if you wear, any nearby creatures will start attacking each other.
 * Deader Than Dead: The Auto Revive up there? It doesn't work if you Well, technically it does, but you just die again.
 * Death by Sex:
 * You turn to stone.
 * A level drain when you're at level 1 will end you.}}
 * Deus Sex Machina: With proper preparation (or, as many like to say, "protection"), seducing succubi and incubi can permanently raise your level or stats and is generally a great resource.
 * Development Hell: The last version, 3.4.3, was released in 2003. Apparently, the Dev Team is still actively developing it, but each version is closed source until the binary is released.
 * The Dev Team Thinks of Everything: The Trope Namer. It even has its own page.
 * See also the bugs list, for things the Dev Team didn't think of.
 * Becomes funny when you realize that most every bug listed seems to be a case of The Dev Team Thinks of Everything. You can't rub a touchstone on gold? Why bother in the first place?
 * Another one might be: Lit potion may survive hero dying from splattered oil burning on the floor. Who the heck noticed that?
 * Also: Sunsword does not work as expected against shades. You aren't running into shades until you are well on your way to ascending and someone actually took the time to figure that out.
 * Diagonal Speed Boost: Naturally, as it's a roguelike. The "grid bug conduct" challenge is for your player to ignore the speed boost, which makes the game a lot harder.
 * Disc One Nuke: In a few ways, be it an early wish or polymorphing.
 * Some players regard "Elbereth" as a disk one nuke. Writing Elbereth in the dust with their fingers will protect the player from almost all early monsters, and many later ones.
 * Due to class special abilities, a Rogue on the very first turn can throw up to 2 daggers at a time. Developing the skill can increase that to up to 4 daggers at a time. Enchanting the daggers (or finding enchanted daggers), plus strength damage bonus, means a Rogue is almost guaranteed to be a long range killer by machine-gunning daggers. This is why Rogues start with a stack of daggers. (The drawback is the Rogue Quest.)
 * Rangers can do the same, but have to find the daggers on their own, as well as develop the skill from scratch.
 * The nearest thing to a guaranteed Ascension is the spell of Charm Monster for Tourists or Wizards. No one ever uses it because:
 * Getting the spellbook is not guaranteed.
 * Requires spell-friendly armor to cast during combat.
 * It takes even more patience than normal Net Hack play. (Which requires a lot of patience.)
 * Do Not Drop Your Weapon: Averted; you can unequip enemies with a bullwhip. One of the few useful applications for a bullwhip, since it is a pretty lousy weapon. Warning, though, enemies can do the same, so if Magicbane is your only source of Magic Resistance, and somebody with a touch of death is around....
 * The player, however, can drop their weapon by eating greasy food without gloves on, and forgetting to use a towel or something to wipe off the grease, leading to Yet Another Stupid Death.
 * Do Not Pass Go: The game displays the message "Do not pass go. Do not collect 200 zorkmids." if you die on your first turn.
 * Dual-Wielding: Blessed + 7 Grayswandir and a blessed + 7 silver saber, yeah baby!
 * Dungeon Bypass: pick-axes can be used to tunnel around enemies and to dig a hole through the floor of one dungeon level down to the next, letting you bypass entire levels at a time (although you will have to deal with the bypassed levels on the way back up -- unless you've got another cunning plan).
 * Dungeon Shop: An important source of items, and (possibly even more importantly) clues as to what the items are (since their appearance is randomized for each game and use-testing can a very Bad Idea).
 * Easily Angered Shopkeeper: The trope was once named Izchaks Wrath, after the only non-random shopkeeper in Nethack.
 * Easter Egg: "You pick up the trapper's tongue. But it's kind of slimy, so you put it back down."
 * "That would be an interesting topological exercise."
 * Too many to list. Most actually overlap with The Dev Team Thinks of Everything in that the player is trying to do something strange, but the game gives an appropriate response instead of simply giving a generic you-can't-do-this response.
 * Elemental Embodiment: Some show up as normal enemies; they can also be summoned, much to the chagrin of anyone messing around with sinks or fountains.
 * Elemental Plane: The late game.
 * Everything's Better with Samurai: Not only can anyone get a katana, but a bunch of items are renamed in Japanese if you play the Samurai class.
 * Everything Trying to Kill You: And the Slash'EM variant is even worse.
 * Even Evil Has Standards: The Random Number God may occasionally give a gnome a Wand of Death, but at least it draws the line at letting monsters use Scrolls of Genocide.
 * Evil-Detecting Dog:
 * Any non-undead pet has the innate ability to detect cursed items and will try its best never to step on them, or to do so only "reluctantly".
 * Also, when you put a leash on them they will whine or act nervous whenever there's a trap nearby, although normally they wouldn't notice.
 * Fair Weather Mentor: The player, almost inevitably. You'll love your pet and give them easy kills and fresh corpses to help level them up, and they'll fight on your behalf... but when food starts getting scarce or you find yourself cornered by a level draining foe, it's every man for himself. There's no penalty for starving your pets to death or abandoning them when the going gets tough except the loss of the pet. Just don't Eat the Dog unless you really have to.
 * Fake Difficulty: Despite Nethack's awesomeness, it is hard not to admit that the game definitely has a share of it. Namely:
 * Trial and Error Gameplay. Described below in detail.
 * Guide Dang It: It would be difficult-shading-into-impossible to win without reading spoilers on some of Nethack's more arcane mechanics. Like all good things, they have their own wiki. Some of the variants, including Slash and Slash'EM, assume you have memorized the guide and up the difficulty to match.
 * Selective Memory: The game provides almost no useful informations about how various spells and items work, what dangers some special monsters present, etc. But how come? Does your character know absolutely nothing about Mazes of Menace? Even if so, why does he/she know nothing about items they bring with them? Well, their types and blessed/cursed status is revealed, but no information is provided about how they actually work.
 * Random Number God. If he gets angry, you are screwed. Well, experienced players have demonstrated that most games are winnable, but you also have to be a very experienced player to agree with it.
 * Unwinnable by Design: if you before, you'll be unable to.
 * Filk Song: Filk singer Rob Balder wrote a song about the game. You can listen to one version of it here.
 * Final Death: All deaths are final, unless you have a certain rare item...
 * Foe-Tossing Charge: The game has many instances when the player is surrounded by monsters and only needs to pass through. In such situations, this trope can be imagined very easily. Especially if you have a wand of teleport. Especially if you have an extra one, so you can break it in two and teleport anything within range.
 * Flat Earth Atheist: The "atheist" conduct involves not using any of the religious elements of the game, satisfying the technical specs of this trope. Of course, actually playing this way pretty much requires you to either know not to do these things, or die before you get to do them.
 * Forgot to Feed the Monster: While food is very common & you usually don't have to actively feed your pet(s), it is possible for them to starve to death. Can also be reversed - if you're hungry, your pet might get to & eat food before you can. Your pet(s) will also go feral if you leave them on a different level for too long.
 * Fourth Wall Mail Slot: On some Unix systems, if you receive a new email while playing, the email is brought to you on a scroll in-game, delivered by the mail daemon.
 * Fun with Acronyms: The fandom has multiple acronyms just for the act of dying, with varying levels of unfairness implied: YASD [Yet Another Stupid Death] is in regard to deaths that were your fault, YAAD [Yet Another Annoying Death] is in regards to deaths that were beyond your control i.e. instadeath attacks, DYWYPI [Do You Want Your Possessions Identified?] which is sighed by many a player on the freenode.irc channel after their death, and GwtWOD [The Gnome with the Wand of Death] which is a disappointingly common cause of YAAD.
 * Gender Bender: Wear unidentified amulets or mess around with polymorphing at your own risk.
 * Genie in a Bottle: In magic lamps as well as (sometimes) actual bottles. Possible source of a wish, if handled correctly.
 * Get Back Here Boss: Most of them can teleport around at will, and will use this ability to run off and heal.
 * Gone Horribly Right - With work, it's possible to genocide a whole range of creatures, the weaker ones. Overdo the blessed scrolls of genocide and all that's left are the very toughest creatures, which aren't genocideable. The final stages of the game become even more exciting, and frequently, much shorter, too.
 * Gratuitous Japanese: Playing a samurai/kunoichi, the game feedback will call certain items by the Japanese name (helmet -> kabuto) or a rough Japanese equivalent (booze -> sake), even though they're literally the same item behind the scenes. The samurai Quest is particularly full of this.
 * Grave Humor: Any grave that wasn't generated by a player's death randomly generates a humorous message. nethack.alt.org added a ton of them.
 * Grave Robbing: Allows you to find gold and items. Slightly less helpfully, lets you find mummies and zombies.
 * Hailfire Peaks: The Valkyrie Quest has both lava and ice in the same map. Explained as the result of Fire Giants invading the naturally frosty Valkyrie homeland.
 * Have a Nice Death: Your tombstone tells you how you died; usually that just means which monster, but sometimes, it's much more unique.
 * For those who don't know where to look for the cause of death... he died by kicking a wall.
 * Sometimes, figuring out just how to reproduce a specific death can be a non-trivial exercise in itself. ("turned to slime by a scroll of genocide", anyone?)
 * It's even possible to have 'elementary chemistry' as a cause of death, if you're careless with acid.
 * Hawaiian-Shirted Tourist: All Tourists start with a Hawaiian shirt, not to mention an expensive camera.
 * Hoist by His Own Petard: The easiest way to kill is with.
 * Holiday Mode: Date, time, and phase of the moon may all affect the game.
 * On Friday the 13th, the start-up message says "Watch out! Bad things can happen on Friday the 13th", and your luck factor is reduced.
 * On a full moon, the start-up message says, "You are lucky! Full moon tonight", and your luck is increased, but dogs may be less friendly, and werecreatures are usually in animal form, especially at night.
 * During the new moon, cockatrices are more dangerous.
 * Between 10 pm and 6 am, some creatures are slightly more dangerous.
 * From midnight till 1 am, undead do twice as much damage, and you get a different message when entering graveyards.
 * Hollywood Acid: Averted in that most acid attacks only cause a few hit points of damage and corrode metal items instead of instantly dissolving them.
 * Horsemen of the Apocalypse: Death, Pestilence, and Famine (referred to as The Riders) make an appearance as endbosses in the Astral Plane. War
 * I Fought the Law and The Law Won: The Keystone Kops will spawn in large numbers if you rob a store. They are among the only monsters in the game that can never be rendered permanently extinct. No matter how many armies of them you defeat, there'll always be another pack ready to jump you NEXT time you step outta line.
 * Implacable Man: Subverted. Once you're high level and well-tooled for melee with AC in the negatives and a ring of regeneration, you can smite an entire room of trolls and dragons, taking blows and regenerating the damage faster than they can dish it out. Then in walks a gnome who puts you to sleep with his wand and beats you to death with his tiny crossbow.
 * Improvised Weapon: Speaking of beating things to death, you can wield nearly any item and use it for the blunt-force trauma if nothing else.
 * Infinity+1 Sword: Grayswandir, a silver saber which deals double damage to all monsters (instead of just some like other artifacts), plus extra damage to silver-hating monsters.
 * Although there are other far more powerful attacks in the game. Especially ranged attacks that can kill enemies before they get close enough to hurt your character. See Storm Damage.
 * That doesn't include the attack spells. Some of which have an area effect repeated multiple times. Like fireball, which is Exactly What It Says on the Tin.
 * Interface Screw: the Rogue level, a Shout-Out to the interface of Nethack's predecessor.
 * The Rogue level is nothing compared to being confused, stunned, or most especially, Hallucinating. When confused or stunned, moving takes you in the wrong direction most of the time. When hallucinating, you can't tell friend from foe.
 * Blinded can sometimes be worse. Being blinded in a shop will guarantee you a YASD. The same with Temples and Towns.
 * Inventory Management Puzzle: You can carry a lot of swag, but eventually, you have to start caching, and if you want to be 100% certain of not losing a cache, you either have to or  And even then, there's probably some way it can go wrong...
 * Your pet will pick it up if you don't place a cursed item on top of it.
 * If it's not a permanent Elbereth, peaceful monsters can wander across it and scuff it out. Then the gelatinous cube shows up...
 * Invisibility Cloak: Available as both a cloak and a ring, as well as intrinsic invisibility conferred by wand (permanent), and potion or spell (temporary). Note that it doesn't make you completely unfindable; monsters will try to guess your location and attack where they think you are. All of the above items can also be used by monsters, making the "See Invisible" intrinsic very important.
 * Just Add Water: Several types:
 * Dragon scales (dropped by dragons) + Scroll of Enchant Armor = Dragon Scale Mail (one of the best armor choices)
 * Wielded Worm tooth + Scroll of Enchant Weapon = Crysknife (a Shout-Out to Dune).
 * Alchemy: mixing less-useful potions can generate more-useful potions (and vice versa).
 * Once you know a scroll or spellbook, you can write more copies with a magic marker on a blank scroll or spellbook. On the other hand, magic markers are hard to come by and often have to be wished for.
 * Katanas Are Just Better: they get +1 to hit for no particular reason.
 * Ki Attacks: The Monk gets these in Slash'EM.
 * Kick the Dog: You can do this if you like, literally even. You Bastard. Seeing as your pet is your loving sidekick and in fact one of your more useful assets, this is usually an accident when it happens.
 * Kitchen Sink Included: With a surprisingly large number of gameplay uses.
 * Level Grinding: The "pudding farming" method allows you to collect massive amounts of hit points -- as well as really good loot.
 * Also contains Anti-Grinding -- leveling up too much before you find good equipment is a good way to get yourself into trouble.
 * Level Scaling: Bases the level of enemies you'll face on the average of your character level, and the depth you've reached in the dungeon.
 * Logical Weakness: Tridents do additional damage to aquatic monsters. Axes do extra damage to Wood Golems. Clay Golems can be destroyed in one shot if you've read the original folk tale and . The list goes on...
 * Luck-Based Mission: Luck plays an important role in Nethack; if the Random Number God wants to kill you, it probably will, because, at any given moment, there are many things that can go wrong. Taking precautions that will let you survive its wrath is an important part of the game.
 * Christian Bressler, aka 'Marvin the Paranoid Android' ascended 23 times in a row over a three month span on the public server NAO, mostly to show that any individual game could be won. Including one of every class for the first 13, then he started doing conducts.
 * Adeon, another NAO player, ascended 29 times in a row over the course of just barely more than one month.
 * ais523 did prove that it's theoretically possible to die before you have control of your character, the very definition of an unavoidable death. He did some calculations and estimated a 1 in 3 million chance (roughly) of this occurring.
 * One of the various traps that an adventurer can encounter is a pit. Sometimes, this pit has spikes. Sometimes, these spikes are poisoned. And sometimes, poison is instantly lethal. Therefore, characters who don't possess poison resistance could theoretically die at any given moment, should they wander into a trap such as this.
 * The truly paranoid will try to only step where they've seen other monsters step safely, or search when that's not possible.
 * Macrogame: Bones files -- a good argument for playing on an online server.
 * Magikarp Power / Lethal Joke Character: The tourist character class. Arguably, all the "weak" character classes have this to some extent - but it's most noticeable with the tourist, who might (arguably) be the easiest role to win with if you survive past the Quest. But that's a big "if."
 * To elaborate, the Tourist starts with a stack of throwing darts, a flashy camera, some money, a pile of food, two healing potions, and some scrolls that are useful only in the endgame. He does not start with any melee (or non-expendable) weapon, any spells, any armor, or decent combat stats in case he comes across either of the above, and shops will vastly overcharge him for the first half of the game. If he survives to the quest, though, his reward is effectively an infinite-use blessed scroll of charging (which also grants magic resistance, super-telepathy, and half damage from enemy magic just by having it in your inventory), which means double or triple the duration of most wands, easy creation of + 4 or + 5 rings, and infinite uses of most tools (including a food generator, an enemy tamer, and some that mimic offensive wands). And to top it off, your useless starting shirt and scrolls become valuable in the endgame, and the stats that start the highest for him are the hardest ones to increase later on.
 * Throwing darts are a ranged attack, which is always good. There are plenty of dart traps to untrap for more darts. Poison them with a potion of sickness and they can be a big help.
 * Magic Pants: Averted: if you change into a much larger form, then the armor you're wearing will be torn apart and destroyed.
 * And if you turn into something exceptionally weak and puny, you'll be half-squashed by the same armor and unable to move.
 * Actually, there are no pants in Nethack whatsoever. This still confuses newbies.
 * If you sit on a cockatrice corpse, you don't turn to stone, so you must be wearing pants. Since they don't tear apart or anything, they must be magic. So the pants are magic, but it's averted with the rest of your clothing.
 * Mailer Daemon: A literal one; it delivers messages from other users on the system.
 * The daemon normally appears and disappears within one turn without giving a chance for the player to interact with it. However, a Crazy Prepared player can kill it, preventing further messages from being delivered; to do this, the player needs to.
 * Make a Wish: The most certain, and in some cases only, way of getting some desirable rare items. On the other hand, it may be much more useful to wish for an item with an important Mundane Utility.
 * The Many Deaths of You: There are many (many many) ways to die, leading to a lot of Trial and Error Gameplay. Some can only realistically be obtained by deliberately setting out to collect them.
 * Medusa: A boss.
 * Mini Game:
 * The Sokoban branch. Interestingly, the Mini Game is done with the same mechanics as the rest of the game, with only minimal changes (boulders can't be pushed diagonally, and you can't fly over holes in the floor).
 * And certain other things (i.e. using spells to get rid of boulders) will give you a luck penalty.
 * One way to enter the Castle is by winning a game of Master Mind.
 * In the endgame, wielding the Amulet of Yendor lets you play hot/cold to find the hidden portals to the next level.
 * "Mother, May I?" with the Quest Leader.
 * Minesweeper in the Ft. Ludios treasure room. (Although this may be more of a Shout-Out.)
 * Metagame: Many sort-of-intentional deaths are caused on the first few levels by people repeatedly seeking some early advantage, such as quaffing from fountains (it’s supplication to the Random Number God for a wish, in case you’re curious), or kicking sinks for a ring and then dying if a foocubus/black pudding comes up and they can’t handle it (or don’t want to waste time handling it). This is a form of startscumming, and not everyone thinks it's a-OK.
 * Mighty Glacier: Mumakil. Their cousins baluchitheria, as well, to a degree, but.
 * Mission From God: The Excuse Plot.
 * Money for Nothing: There are things that are worth spending gold on, but the fact that you can kill almost anything you gave your gold to means that generally, once you're done with getting your protection, you're more or less done with money as well.
 * Monsters Everywhere: Horses, bees, trolls, elves, snakes, demons - and everything in between - grows out of rock. Or perhaps they are spawned by the evil Wizard. But why then does he spawn a puny rat to defeat the hero that just killed five dragons without breaking a sweat? Maybe to maintain a certain ambiance? Kitten and Vampire Lord fights side by side!
 * Mook Bouncer: The Quantum Mechanic has a "teleport" attack.
 * Mushroom Samba: the hallucination effect, obtained by drinking a certain type of potion, eating the corpses of some monsters (including several fungus monsters), and an exploding black light causes nearby monsters and items to appear as random other items or monsters that don't actually exist. It also gives alternate messages for some other effects.
 * Needle in a Stack of Needles: One of the things the Wizard can do to make your life more difficult is steal the Amulet of Yendor. And then leave fake ones. Do not try to enter the endgame without the real one...
 * Quaffing a cursed Potion of Gain Level on dungeon level 1 is a failsafe way to exit the Dungeons of Doom. If the player's not carrying the Amulet of Yendor, he/she just "feels uneasy." If he does have the amulet, it's up and out. The Dev Team Really Does think of everything.
 * Neglectful Precursors - The DevTeam, of all people. There hasn't been an update to the game since December 8, 2003. (The previous longest time without a release of any kind is three years.)
 * Nerf Arm: Cream pies are surprisingly useful as weapons, and you can eat them.
 * Nintendo Hard: To the point where there is no shame in dying on the second or third level if you're a new player. One can die in less than 50 turns if they don't know what they're doing, and it's not unheard of for players to die on their first turn.
 * Non-Human Undead: Zombie and mummy giants, elves, dwarves, orcs, and gnomes along with the regular ol' human variant. You can also zap most corpses with wands of undead turning to bring monsters and animals back to life.
 * Nostalgia Level: The Rogue level, a reference to the original "Roguelike", is presented in black and white, with different symbols for various features and objects, and even some changes to game mechanics (such as monsters not leaving corpses).
 * The Nudifier: The scroll of destroy armor (and the destroy armor spell used by certain monsters).
 * Olympus Mons: A high-ranking angelic being and an uber-powerful undead mage can both be your pets, despite possibly being powerful enough to destroy your character several times over. With a bit of work, even two of the horsemen of the apocalypse can be brought under your control.
 * One-Hit Kill: Tons of em, on both sides.
 * A Wand of Death, the Finger of Death spell, a bad roll on a poison check, doing anything that involves your bare skin and anything even tangentially related to a footrice including as their eggs, hitting a Floating Eye in some cases, encountering a soldier ant/leocrotta/mumak/minotaur when unprepared for melee, Medusa's gaze. A drowning attack is technically a two-hit kill but feels like a one-hit kill.
 * Optional Sexual Encounter: Succubi and incubi again. The page image for that trope is from this game.
 * Our Werebeasts Are Different: Werewolves, wererats, and werejackals.
 * Pacifist Run: It is possible for a very skilled player to win the game without personally killing anything.
 * Pet Interface - a surprising amount for tame monsters.
 * The safe_pet and highlight pet options.
 * Carrying pet treats in open inventory (tripe for dogs/cats, pears/apples for horses) means your pet will stay much closer to you.
 * Tossing your pet a treat reinforces its recent behavior. You can train your pet to steal from shops!
 * A leash physically keeps your pet close to you, even when going up/down stairs or dropping through holes. (You can use multiple leashes, too.)
 * A tin whistle will kind of call your pet to you. A magic whistle will teleport your pet(s) to your side if they're anywhere on the level.
 * #chatting to your pet can tell you about their condition.
 * Pets are reluctant to step on a square with a cursed item on it (unless there's food there they want.) This can identify cursed items. It can also be used to control a tame animal's movement.
 * You can 'a'pply a bullwhip at a humanoid pet to take their weapon away. (For replacement with a better weapon.) You can also prepare and leave weapons, armor, and tools for your humanoid pets to pick up and use.
 * Wand of probing tells what a monster (tame or otherwise) is carrying.
 * A stethoscope tells an animal's basic Hit Points and its speed.
 * Spells of healing and extra healing can be used to heal pets.
 * Breaking a potion of regular, extra, or full healing can heal pets.
 * Saddles permit horses, dragons, and some other monsters to be ridden.
 * Press Start to Game Over: If you're very unlucky with the Randomly Generated Levels, it's possible to die on your first turn, and there's even a special Have a Nice Death message for it.
 * Psychic Radar: Telepaths can, when blinded in any manner, see the exact location of any monster on the current floor that can think.
 * Public Domain Artifact:
 * Random Number God: The Trope Namer.
 * Rare Candy: Potions of gain level and wraith corpses give level-ups. Potions of gain ability (especially blessed) and the "gain ability" effect of magic fountains increase stats.
 * Ret-Gone: A scroll of genocide not only kills all monsters of a given type, it removes them from reality. If you genocide cockatrice and you were holding a cockatrice in your hand and three of their eggs in your backpack, they'll all vanish. If you had a tin filled with red dragon meat and you genocide red dragons, that tin mysteriously becomes empty. And you'll find yourself unable to polymorph into one now, even if you had already done so before. Also, if you genocide your own race/role while polymorphed, the game will say "you feel empty inside". Try to turn back and you will die. If you quit before dying, the game will read "quit while already on Charon's boat."
 * Required Secondary Powers: Scrolls of fire and books of fireball can't burn, Wands and books of cancellation can't be canceled, wands, potions, and books of polymorpth can't be polymorphed. The idea being that immunity to the effect they contain is necessary to contain it in the first place.
 * Rogue: Nethack's predecessor.
 * Rule of Three: There are three end game bossess to fight.
 * Save Game Limits: The game only allows one savefile per character. If you want to make backups to protect against crashes, you'll have to do that manually. Any other use of backups is considered very bad form.
 * Save Scumming: Like just about any roguelike, Nethack erases your save upon death. Instead, some players will "start scum," repeatedly starting and quitting the game until one gets a favorable set of starting equipment or stats. This is usually done with wizards, due to the ridiculous magical items a lucky wizard can start the game with (pre-ID'd to boot). A little over 50% of all NAO games are turn-0 quits, a good portion of those wizards.
 * Schizophrenic Difficulty: Despite dangers like arch-liches, mindflayers, and, the game gets much, much easier after the first dozen levels or so due to the necessity of being Crazy Prepared and to vastly overpowered early monsters like soldier ants, leocrottas, and chameleons.
 * Sdrawkcab Name: Yendor...
 * The Wizard of Yendor is affectionately referred to as Rodney as a consequence, which is Yendor backwards.
 * Sealed Room in the Middle of Nowhere: Where you end up if you teleport by accident into a vault. Sure, there's a guard who comes along to check it, but if you refuse to give up all your gold, you're stuck inside until you starve to death.
 * Self-Imposed Challenge: lots of them, and the game keeps track of which restrictions you've managed to not yet break.
 * Shapeshifter Mode Lock: This will happen if you genocide your race/role while polymorphed. Try to change back and you will die. Also, Amulets of Unchanging can be worn for this effect.
 * Shout-Out: Rogue in the form of the Rogue level, includes a lot of Dungeons and Dragons and Lord of the Rings references, and many more.
 * Fighting monsters while hallucinating generates a ton of them.
 * The Tourist class is basically one big Shout-Out to Discworld. The quest leader's name is even Twoflower!
 * Sidequest: the Gnomish Mines, Fort Ludios, and Sokoban can be skipped.
 * It might actually be impossible to visit Fort Ludios in a given game.
 * Skeleton Key: Any key found will unlock any door or chest (older versions had different kinds of keys that could only open corresponding types of locks).
 * Songs in the Key of Lock: One way of getting into the Castle. A (possibly unintended) side effect allows you to easily kill off most of the monsters in the castle:
 * Sorting Algorithm of Weapon Effectiveness: Somewhat subverted, both for good and ill as far as the player is concerned.
 * Spikes of Doom: You fall into a pit! You land on a set of sharp iron spikes!
 * Silliness Switch: Hallucinations, caused by magic or dodgy food. Non-hallucinating silliness includes kitchen sinks, tourists, cameras, Hawaiian shirts, and even the Keystone Kops.
 * Stat Death: If your Intelligence drops below 3 (usually by mind flayer attack, although there are other ways to do this), you "die of brainlessness".
 * Stuck Items: Cursed armour can't be removed, and cursed weapons can't be unweilded. There are several ways of dealing with these problems, only 1 ("remove curse") obvious.
 * Stupidity-Inducing Attack: Mind Flayers have an attack that reduces intelligence.
 * Suffer the Slings: An available weapon; although not particularly effective, at least the ammunition is easy to come by.
 * Super Drowning Skills: You can cross water by almost every conceivable method except swimming.
 * Including, it should be noted, donning an amulet of magical breathing and walking along the bottom.
 * Thankfully, non-aquatic monsters seem to also have Super Drowning Skills.
 * Super Weapon, Average Joe: Humanoid monsters can find and use wands. This can lead to very weak monsters killing the player with ease. Fans refer to this happening as "gnome with a wand of death".
 * Super Weight: You start at zero or occasionally one on TV Tropes' scale. Except for the Tourist, who starts at negative one. You spend the game climbing the scale.
 * Taken for Granite: From the cockatrices, one of the game's many Goddamned Bats.
 * Technical Pacifist: See Pacifist Run, above, and note that the requirement is that you don't personally kill anything. Leading an army of high-level pets through the dungeon and letting them slaughter everything you meet is just fine.
 * Tech Points: You need both "skill slots" (gained through Experience Points) and a certain number of successful uses of the item/spell in question to advance a skill.
 * Throw the Book At Them: Unusual move, but if it'll save your behind, you shouldn't discount it. Spellbooks can also be wielded.
 * To Hell and Back: The bottom (second) half of the game takes place in Gehennom. Earlier Nethack versions literally had Hell instead.
 * Tomato in the Mirror: "Who do you think you are, ?"
 * Too Awesome to Use: Averted with a vengeance, since you practically have to use powerful items early and often to survive at all. If you come in with the hoarding attitude, it can take a while to get used to the idea that it's OK to use two charges from your wand of fire on dungeon level three as long as you don't die.
 * One clear example, the scroll of Scare Monster. You get one, maybe two uses before it crumbles to dust. Early on engraving Elbereth in the dust works almost as well, and is repeatable. Late game opponents aren't affected by the scroll.
 * Very useful if you get blinded, however.
 * Touch of Death: A couple of high-level monsters can do this. Getting the proper preventative gear is a early-game priority.
 * Trial and Error Gameplay: The player is supposed to make out most gameplay mechanics this way. In a game with an immense game world, permanent death, and most errors leading to said permanent death. No wonder that players doubt the possibility of ascending (winning the game) without reading spoilers. The game does provide an Oracle, a special monster which gives valuable advice about the game, but it has great limitations on its consultations.
 * Turn Undead: Available through a spell, a wand, and a class attribute. Due to liberal application of Just for Pun, you can also use it to Very useful when
 * Underground Monkey: The standard game is constructed entirely of ASCII characters, leading to a lot of creature-overlap. You definitely still don't want to confuse a dwarf king with a mind flayer (both are a purple h). Or a mordor orc with a floating eye (one a dark blue o, one a dark blue e.) Various alternate tilesets can be used to supply more information.
 * Unicorns of varying alignment.
 * Unexpected Gameplay Change: The Rogue Level, which is a level that resembles Rogue.
 * Unusable Enemy Equipment: Averted. If a critter has it, you can kill him and use it. (An exception being said critter's body; you may or may not get a corpse.)
 * Averted only if it's not used on or against you first... This is particularly frustrating with Auto Revive, as monsters can use it too. Or the Wand of Death. Or that potion of gain level. The monsters would love a chance to use their equipment. And they'll pick it up off the floor to hand it to you.
 * Monsters have a starting inventory and also death drops ("That was my prized wand of nothing, You Bastard! I was saving that!" grunts the orc), though sometimes it can be hard to tell the difference if the monster dies without a chance to use the item.
 * Video Game Caring Potential: Helping a monster out of a pit might make it peaceful, and you also might get an alignment boost if you're Lawful.
 * Video Game Cruelty Potential: Have a chat with the nurses. They're not mean! They'll go right on trying to get you to take off that armor and put away that weapon. They'll heal you! And they'll keep trying to heal you even as you chop them up and tin them with your tinning kit.
 * Video Game Cruelty Punishment: Your patron god has very firm ideas on what is and is not right action. This doesn't mean you're supposed to be well-behaved. It means you're not supposed to be caught.
 * Or, in some people's minds, it means surviving the very wrath of God. Which is doable. And best of all? If you do, your god says "I believe it not!"
 * Wafer-Thin Mint: If you're satiated, then eating anything - even an insubstantial wraith corpse - has a chance of causing you to choke to death... and that wraith corpse doesn't give the player a warning beforehand.
 * We Buy Anything: Averted. Most shops specialize and will only buy what they sell, and all shops have a limited amount of money with which to buy stuff from the PC, although shopkeepers will offer store credit instead when they can't pay you in cash anymore.
 * Played straight in that any shop will sell the player anything that comes into the shopkeeper's possession. This can be useful for price identification.
 * Weak but Skilled: Several classes. Also a good mindset for the player themselves, especially in the early game.
 * Weapon of X-Slaying: Orcrist and Sting (orcs); Ogresmasher, Giantslayer, Werebane, Demonbane, Dragonbane, and Trollsbane (Exactly What It Says on the Tin); Scepter of Might (non-coaligned monsters); Sunsword (undead); Vorpal Blade (jabberwocks - it always decapitates them, instead of the normal 5% chance per attack).
 * A Winner Is You: If you fight, sneak, and fast-talk your way through 45 to 53 levels of Everything Trying to Kill You, both ways, plus 5 bonus endgame levels, over what can be weeks of playtime and hundreds of thousands of moves, you get this:
 * [[spoiler: An invisible choir sings, and you are bathed in radiance...--More--
 * Weak but Skilled: Several classes. Also a good mindset for the player themselves, especially in the early game.
 * Weapon of X-Slaying: Orcrist and Sting (orcs); Ogresmasher, Giantslayer, Werebane, Demonbane, Dragonbane, and Trollsbane (Exactly What It Says on the Tin); Scepter of Might (non-coaligned monsters); Sunsword (undead); Vorpal Blade (jabberwocks - it always decapitates them, instead of the normal 5% chance per attack).
 * A Winner Is You: If you fight, sneak, and fast-talk your way through 45 to 53 levels of Everything Trying to Kill You, both ways, plus 5 bonus endgame levels, over what can be weeks of playtime and hundreds of thousands of moves, you get this:
 * [[spoiler: An invisible choir sings, and you are bathed in radiance...--More--
 * With This Herring: The Tourist class is the most obvious example, but several other classes qualify.
 * Wizard Needs Food Badly: In an exception to Bottomless Bladder, the PC needs to eat, with the PC fainting if s/he gets hungry enough, and eventually dying of starvation. If your character class is a Wizard or Valkyrie, or your character race is Elf, the game will actually use this phrase, in one of the game's many Shouts Out.
 * A Worldwide Punomenon: Levitating characters will sink if they float over a sink. Drinking a cursed potion of gain level causes a character to move up a dungeon level. Scrolls of mail, on UNIX systems, are delivered by a mail daemon. If you try to identify a wand of striking by engraving something on the floor, you'll receive a message that it "unsuccessfully fights your attempt to write."
 * Yet Another Stupid Death: The Trope Namer.
 * You Will Not Evade Me: Once you've found him and woken him up, The Wizard of Yendor will reappear periodically wherever you are, and taunt you for thinking you could elude him (if he was alive and on a different dungeon level). A slightly different taunt appears if he was killed instead (he revives after a while). Several high-level monsters, including the Wizard, will teleport to your location if you try to run away from the fight but are still on the same level. All of them combine this with Get Back Here Boss, for maximum annoyance.