NetHack

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

- Battlereports.com user Johnny_Vegas in his report of a NetHack game posted on March 23, 2006.

NetHack is old. It began life in 1987 as an online version of Hack, and even now its development is still in progress.

NetHack is complex. It can take years of play to see it all, and more still is being added.

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 - singularly or in combination. The advantage of a focus on items is that it reduces the impact of luck: By carefully hoarding your resources, (almost) nothing is inescapably fatal. The downside of a focus on items is that it reduces the impact of luck: Once you've learned some effective tactics, multiple play-throughs 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 far 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 download it directly from their official website or even compile it yourself using the official repository on GitHub.

You can also play it online here, at Hardfought, or on various other public servers - you can even use a telnet or SSH connection to connect and play from a compatible terminal. The latest released version is 3.6.6 and all entries apply to that version, although NetHack 3.7.0 is in rolling release Open Beta, meaning that it is available to play on Hardfought as it is being developed. Older versions of the game can also be downloaded from the main site as well - 3.4.3 in particular still has quite a bit of popularity as a result of it nearly being the "last" version ever, and is additionally hosted on Hardfought.

You can find the main wiki here; the old Usenet group (which is now a part of Google Groups) is located here for your perusal, with a mirror located at the NetHack Patch Database on bilious.alt.org. A dedicated NetHack Reddit can be found here, and IRC chatrooms for discussing the game itself can be found on Libera.chat at #nethack and #hardfought among others. A scoreboard for tracking playthroughs can be found here on its own dedicated site.

Naturally, the NetHack General Public License means that there are multiple variants (the community term for forks and mods) of the game, each with their own relatively unique flavoring, such as SLASH'EM, SporkHack and UnNetHack. Some such variants arose in response to the belief that work on the official game had ceased as result of its post-3.4.3 Development Hell - many are still actively developed alongside the main game, and even borrow updates and changes made there as well. One highly recommended variant on the original game is DynaHack, which not only adds new content, but also includes an in-game tutorial and a friendlier user interface, which makes it perfect for beginners.

As stated above (and quoted by Christopher Wellons in his blog post "Play NetHack" on nullprogram.com), NetHack's rather archaic ASCII belies the amount of gameplay depth it truly holds. That said, if ASCII intimidates you or you simply have a different preference, 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 official site is down, but there are forks; Vulture has builds for vanilla NetHack, SLASH'EM and UnNethack. Additionally, the NetHack Wiki has a list of other alternate graphical tilesets.

'''Important Note: Spoilers are easily accessible via the wiki and IRC, but there is always the difference between knowing of something and experiencing it for the first time - even so, in the spirit of being as new-player friendly as possible, potential spoilers are marked as best as possible. The NetHack community defines "spoilers" as not just including plotline spoilers, but gameplay-related ones as well. The plot itself usually has far less direct impact on the game than its various mechanics, so if you wish to experience as much of the challenge as possible, read with caution and mind the spoiler tags and links.'''


 * The Dev Team Thinks of Everything: It even has its own page.
 * There's also the bugs list, for things the Dev Team didn't think of, though it becomes funny when you realize that most every bug listed seems to loop back around into examples. You can't rub a touchstone on gold? Why bother in the first place? Lit potion may survive hero dying from splattered oil burning on the floor... Who the heck noticed that?
 * The undead-purging Sunsword didn't work as expected against shades, who are immune to all weapons that aren't blessed or silver. A player normally wouldn't run into shades until Gehennom, at which point they have even more viable weapons. Someone actually took the time to figure that out - and as of version 3.6.0, it's been fixed.
 * Random Number God:
 * A term coined by the NetHack community, as noted in the "Deification" section of this article on the wiki. The term originated from the "rgrn" Usenet newsgroup, with archives of the FAQ (formerly maintained by Dylan O'Donnell) going back as early as February 2002.
 * The November NetHack Tournament held on Hardfought includes a DevTeam quest that "demonizes" RNG instead: the quest's sole level features a statue of a balrog named RNG near the center.
 * Yet Another Stupid Death: Also coined by the NetHack community during the Usenet days, often shortened to YASD. And best believe there are a lot of stupid ways to die. The wiki even has a list imported from the #nethack channel bot!


 * Shoplift and Die: The trope was once named Izchak's Wrath, after the only non-random shopkeeper in NetHack.

{{quote|NetHack is a game, so you 1337 H4XX0RZ can just go... away.}} {{quote|A golden naga hatchling wriggles out of your pack! Its cries sound like "Mama."}} {{quote|"Thou hadst best fight better than thou canst dress!" "Twixt thy cousin and thee, Medusa is the prettier." "I first mistook thee for a statue, when I regarded thy head of stone."}}
 * Ability Required to Proceed: Downplayed - many levels optional and otherwise do require a certain means of traversing them to continue on, but the exact means varies with the level and the ability of the player, and there's always at least a couple of ways around a given obstacle.
 * The Quest requires that players have a sufficiently good alignment record and be at least XL 14 (by which point you've likely already passed the required alignment threshold, barring some serious misfortune).
 * Least downplayed in the End Game.
 * Absurdly High Level Cap: The experience level cap of 30 is considered this, as you can easily ascend with around half of that (note that you must be XL 14 to enter The Quest).
 * 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, acquired through various means.
 * Action Bomb: The sphere class consists mostly of these type of Mooks. Gas spores explode upon dying normally, which can easily kill low-level players, and spheres attack by exploding their energies directly at the player character.  Lights are a class of monster  that can also explode at the player to impair their sight.
 * 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 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:
 * 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. There is also an encyclopedia that can be used to look up interesting quotes associated with certain monsters. Local installations of NetHack also provide you with a handy more-accurate guidebook in PDF and .txt form, which is also accessible from NetHack's official site.
 * All There in the Script: NetHack is a prominent example of a game that enables (if not encourages) "source diving" to get answers to questions about the deepest workings of the game; this began when the earliest versions of Hack were published, with the BSD-style licensing allowing for distribution.
 * The NetHack site's archive page has the source code for all versions, and their main page has download links going back all the way to 3.2.3/3.3.0. Both the official repository and the wiki have annotated codies of the code that can reveal other things about the setting, monsters and characters (e.g. the fact that ).
 * All Trolls Are Different: They come with enhanced Regenerating Health and Resurrective Immortality that lets them come back to life as long as any part of their flesh remains. They also tend to generate with polearms.
 * Amazing Technicolor Population: The main form of distinguishing between different types of monster within the same class (i.e. using the same symbol) is by their glyph's color. Also implied in particular with the Wizard quest leader's encyclopedia entry.
 * Ambiguous Syntax:
 * No, the spell "Turn Undead" doesn't actually turn you undead..
 * Amplifier Artifact: The Magic Mirror of Merlin exclusively gives Knights double damage to most of their spells in addition to its other intrinsics.
 * 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.
 * And Your Reward Is Clothes: T-shirts, Hawaiian shirts and regular gloves are among the many types of armor you can encounter. Not that they're any less useful; enchanted shirts can provide a light and nifty source of extra AC, and this also holds true for gloves.
 * An Ice Person:
 * The Valkyrie's special spell is cone of cold, and the role always starts with cold resistance.
 * has a special cold ray attack similar to the cone of cold - it has a melee-range variant that does devastating cold damage, potentially enough to kill all but the most powerful characters in one strike! The attack is completely nullified by cold resistance, thankfully.
 * Anticlimax Boss:
 * The Valkyrie quest nemesis Lord Surtur is essentially a more powerful fire giant with many abilities common to both them and other quest nemeses, but isn't particularly difficult for a prepared Valkyrie player character, who is generally played with a heavy focus on good weapons and armor. The stage itself where he is encountered is often considered more hazardous due to the presence of lava and the fact that drawbridges can be broken.
 * The Goblin King in the days when Elf was a character class.
 * The Rogue quest nemesis known as the Master Assassin, especially compared to the quest levels before him. The most difficult part of defeating the Master Assassin is actually reaching him: Like Lord Surtur, he is easy to actually bring down in combat, especially with a storm of daggers.
 * Prior to 3.6.1, Vlad was so anti-climatic that it had become a Running Gag to Cherry Tap him to death with -3 throughly corroded orcish daggers, thrown scrolls, and other such things; many would even name the object(s) in question "Vladsbane".
 * Anti-Frustration Features:
 * The renameable "fruit" (called "slime mold" by default) and various food rations are classified as vegan food, making vegan/vegetarian conduct much easier.
 * The #tip extended command was introduced in 3.6.0 and allows players to empty out the contents of a container onto the floor - its primary purpose is to provide a means for players wielding a cursed two-handed weapon to still access stashed items within a container in spite of lacking a free hand to open it.
 * Seven candles are needed towards the late stages of the game in order to, but there are very few guaranteed sources of candles outside Izchak's shop in Minetown, and even then he may not stock enough of them (whether due to bad luck or bones). As of 3.6.0, the top level of Vlad's Tower contains two stacks of 4-8 candles, and as the level was already ineligible for bones, there will always be enough candles.
 * The Random Number God may occasionally give a gnome a wand of death, but at least the game draws the line at letting monsters use scrolls of genocide.
 * Anti-Magic: Magic resistance is a rare and valuable property that nullifies most of the damage and adverse effects from many magical sources, though it doesn't protect your inventory from them. It does, however, nullify rays and touches of death, and protects you from many trap effects.
 * The cancellation effect can rob most monsters of their magic and some other special abilities; when zapped at objects, it turns some items into their mundane equivalents while removing enchantments (including blessings or curses) from others.
 * Arbitrary Skepticism:
 * The atheist conduct requires absolutely no interaction with religion or the gods whatsoever, despite them very definitely existing in-universe and the goal being . Ironically, the Priest role is best suited for the conduct, since they start the game with holy water (an atheist Priest with holy water, try and figure that out) and have intrinsic knowledge of whether items are blessed or cursed without needing to use an altar.
 * A popular patch included in some variants allows an atheist player to {{spoiler|invoke the Amulet of Yendor and openly defy the gods, returning them to
 * Armies Are Evil:
 * The Wizard of Yendor has command over an evil army, as do other bosses like Croesus.
 * In some games, a horde of orcs will have pillaged Minetown and left it in ruins; this "Orc Town" contains named orcish monsters, up to and including the captain, that are also spread throughout the Mines and the rest of the dungeon. These orcs carry various items and loot that would normally appear in the town otherwise.
 * Armor Is Useless: Averted - better quality armor tends to have a higher AC stat which lowers monsters' hit rates and damage against you. Even more mundane items such as gloves can be handy for additional defense. That said, there's a point where jacking up your AC has diminishing returns, and if a particularly strong monster manages to land a hit, you can still take loads of damage - minotaurs have been known to pulp Valkyires with more than -20 AC and their half-damage quest artifact!
 * Artifact of Death: Downplayed - artifacts can "blast" players that are not of the correct role or alignment for them (especially if they're intelligent), which can potentially instakill weaker characters.
 * Artifact Title: Most people nowadays probably won't know NetHack is an open source port of Hack developed on the then-new Internet unless you ask, to the point that newbie hackers on IRC have constantly mistaken the #nethack channel for an actual hacking forum for years! To quote the topic from #nethack on Libera:
 * Artifact Title: Most people nowadays probably won't know NetHack is an open source port of Hack developed on the then-new Internet unless you ask, to the point that newbie hackers on IRC have constantly mistaken the #nethack channel for an actual hacking forum for years! To quote the topic from #nethack on Libera:
 * Artistic License: Biology: Nutrition in NetHack is... strange to say the least if you try to compare it to real life. While drinking is entirely optional and Nobody Poops, you'll still have to eat regularly, and only overeating can cause you to choke (though it does abuse dexterity). Various other subtropes and examples include:
 * All Animals Are Dogs: Domestic animals can be tamed by throwing the appropriate food at them, and the only way to tame most other monsters is with a scroll of taming (or in some cases by wishing for a figurine). Among other things, tamed monsters will follow you around, attack other monsters they deem threats, and can even be put on a literal leash! Throwing food (especially treats) to an already-tamed monster will increase their tameness, as long as it's food they'll eat, and only tame pets have to worry about hunger.
 * Diurnal Nocturnal Animal: Monsters (including you) only sleep in special circumstances that aren't tied to the time of day - which the game does check, albeit for other reasons.
 * Misplaced Vegetation: You can find trees in most of the quest branches, which are usually outside... and also in the underground Minetown. Perhaps they were planted as decor?
 * More Predators Than Prey: Carnivores and omnivores make up most of the monster roster; in comparison, there are relatively few herbivores, and actual plants are rare, with most of the "plant" life being fungi. Among other things, it seriously cuts into the list of vegetarian-friendly food.
 * If an egg hatches while you're carrying it, the resulting young may be generated tame - the odds of it happening even depend on the gender of your character!
 * Ascend to a Higher Plane of Existence: {{spoiler|What happens when you win.}}
 * Asteroids Monster: Puddings divide into two half-HP clones when hit with iron weapons. Gremlins take a cue from the 80s movie franchise, dividing into two half-HP clones upon contact with water. They will also seek out water to multiply themselves with.
 * Attack Reflector: Granted via shield, amulet, or silver dragon scales/scale mail, and protects you and your inventory from the effects of magical rays while deflecting them back in the opposite direction.
 * Auto Revive: {{spoiler|The amulet of life saving. "You die... But wait... Your medallion begins to glow! You feel much better! Your medallion crumbles to dust."}} It doesn't do much to remove what lead to your death, though... and if {{spoiler|you genocide yourself or have your brain eaten by a mind flayer}} you're done for good.
 * Awesome but Impractical: Crystal plate mail is among the highest AC armor in the game and doesn't interfere with spellcasting - but it's also incredibly heavy and somehow fragile enough to break if it's thrown or even just dropped from a sufficient height.
 * Bag of Holding: Subverted with your inventory, which is contained in a non-physical pack and subject to weight limits - beyond that, you can fit as many items in there as you have lettered slots (up to 52 stacks of items). Containers can circumvent this limit, including an actual bag of holding that reduces the weight of its contents when non-cursed.
 * Baleful Polymorph:
 * Stepping on polymorph traps will change your form instantly unless you have magic resistance or a means of polymorph control - this also applies to monsters, and anyone that steps on one is very likely to drop or tear through some of their armor in the process. Polymorph rings cause "polymorphitis" (i.e. changing forms at random), and are often generated cursed so as to inflict this on unsuspecting wearers. Wands of polymorph can inflict this on enemies and can be zapped at yourself - polymorph control can subvert the "baleful" part, thankfully.
 * Sliming can occur as a result of a green slime's attack, and will eventually turn you into a slime yourself, usually ending your game unless it's cured. The messages accompanying your transformation are certainly unpleasant to read.
 * Shapeshifter corpses will also cause whoever eats them to polymorph - be careful leaving them around valuable meat-eating pets!
 * Bandit Mook:
 * Monkeys will attempt to steal from you while attacking, though they may fail and give up; upon a successful theft, they will try to flee with it for a while.
 * Leprechauns and nymphs can steal gold and items from you respectively, and teleport away after a successful steal, making retrieval fairly annoying at best.
 * "Covetous" monsters can steal certain important items from you, such as quest artifacts.
 * Bare-Fisted Monk: Despite not being able to effectively use weapons, Monks can become extremely powerful and deadly. Various other roles can also train their bare-handed fighting skills (or martial arts for monks and samurai), and the weaponless conduct centers around fighting without the use of a traditional wielded weapon.
 * Basilitrice: The cockatrice is a class of creatures represented by the  glyph, and includes its namesake and their younger form, the chickatrice; their encyclopedia entry is a quoted excerpt that touches on their the relationship to the basilisk. They are always hostile and generally infamous for being a source of many a stupid death and several of the game's worse One-Hit Kills - all related to its ability to turn the player to stone. Just bare skin making contact with its body (e.g., bare-handed melee without gloves or being bitten) is enough to turn a victim into a statue, unless they're incorporeal, already made of stone or are acidic in nature. Even a well-armored player character can be turned to stone if bitten.
 * After the bite attack, the cockatrice will attempt a touch attack; if it lands, there is then a 1 in 3 chance that the cockatrice will hiss at you. Following this, there is a 10% chance that you will begin slowing down and turning to stone, losing any intrinsic speed you have in the process. {{spoiler|(On a new moon, this becomes 100% unless you are carrying a lizard corpse.)}} This is a 'delayed instadeath' that can be cured through a few means, so hopefully you have at least one of them available.
 * Even its corpse has this property - touch a corpse without gloves or try to eat one, and unless you're stony or acidic it's game over. On top of that, its corpse is also poisonous to eat, and being hit with or eating an egg will similarly induce a slow stoning. {{spoiler|If you're in a form that's immune to stoning and poison, however, then footrice corpses taste just like chicken!}} Grab a corpse with gloves, on the other hand, and you have an Improvised Weapon that turns non-immune monsters to stone, even including many later bosses! Players tend to call these "rubber chickens", and this can also be done using the eggs as projectiles.
 * ...but intelligent enemies that can wear gloves will do the same to you, if they find a rubber chicken or some footrice eggs. (Thankfully, this is non-instantaneous as above.) There's also the still-present danger of touching the corpse in other ways - better not fumble or fall onto it!
 * Of note is that golems and skeletons are also immune, partly due to being non-living. Golems have their body turned to stone but remain mobile otherwise, while skeletons are completely unaffected - likely as a result of not being bothered by instant fossilization.
 * NetHack variants often add an additional spin on the cockatrice and its kin, some of which even introduce the basilisk itself.
 * Bear Trap: Appears as one of the many traps, and tripping one damages the victim and holds them in place for a while or until they're freed. {{spoiler|Special messages occur if a bugbear or owlbear is caught in one.}}
 * Big Red Devil: The default tileset portrays many of the demons as this. {{spoiler|And strangely, Ixoth the red dragon as well.}}
 * Big Creepy-Crawlies: Most of Team a and  monster classes are composed of unreasonably large multi-legged insects and arachnids. Ants, bees, beetles, spiders, you name it!
 * Blade on a Stick: Several of the polearms qualify - glaive, bardiche, voulge, bill-guisarme, partisan, halberd, fauchard...
 * Blindfolded Vision: Invoked with intrinsic telepathy, which is heavily desired by zen players. It's also possible with extrinsic telepathy, and is a solid option to protect against gaze attacks while still being able to fight effectively.
 * Blinding Camera Flash: Expensive cameras can be found, and their purpose is to blind and scare monsters with the flash. {{spoiler|It's also one of the very few things that can make the Riders flee from you, outside of things like a tooled horn.}}
 * Block Puzzle: Sokoban, a four-level puzzle branch based on the game of the same name in which you push boulders to plug holes in the floor. The game mechanics are somewhat different: You can't push the boulders diagonally or fly over the holes in the floor, and it is possible to destroy the boulders (or create more) at the cost of a Luck penalty.
 * Bloodless Carnage: It is an ASCII game, and there's certainly no mention of it in any of the battle messages. May be averted depending on your choice of tiles, though.
 * Bolt of Divine Retribution: Tick off a god enough, and you'll get struck by lightning.
 * If you manage to {{spoiler|survive that, the deity will then blast you with a wide-angle disintegration beam. If you still manage to survive, the deity will exclaim in shock "I believe it not!"}}
 * {{spoiler|And if you're being digested by a monster at the time, then the lightning will hit the monster you're inside of, almost certainly killing it instead of you. If the monster survives the bolt, it gets hit by the disintegration beam too (although the only monster in Vanilla that engulfs and resists lightning also resists disintegration). You even get experience and break any pacifist conduct for doing so.}}
 * Boss in Mook Clothing:
 * Liches. They can curse your items and lower your strength, their cold touch can destroy potions in your open inventory, and the stronger ones can teleport after you and even use a Touch of Death! {{spoiler|And they're eligible forms for chameleons, likely the earliest shapeshifters you'll run into.}}
 * Archons, titans and ki-rin are devastatingly powerful foes that appear very rarely in the dungeon. On average, barring shapeshifter shenanigans you'll only ever see them late in the game, at which point you'll understand just why that is - they're nasty summoners, can curse your inventory and even death-touch you in some cases, and each has their own ability that can cause you no end of trouble, be it the archon's dazzling gaze or the titan's Super Strength.
 * 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 in theory, but is mostly just there as a hazard.
 * Wizard Needs Food Badly: In an exception, the PC still needs to eat, and will begin fainting if they get hungry enough, eventually dying of starvation. If your character class is a Wizard or Valkyrie, or your character species is elven, the game will actually use this phrase, in one of the game's many Shout-Outs.
 * 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 such as darts, arrows, and slung rocks have a chance of breaking when thrown. Katana wielded by samurai and two-handed weapons have a 5% chance of shattering an enemy's wielded weapon and causing them to flee.
 * Bribing Your Way to Victory: Downplayed - throwing a significant amount of gold to hostile Yendorian soldiers or watchmen can be used to pacify them and get them off your back for the moment. {{spoiler|A different type of bribing can also be done with Asmodeus and Baalzebub, though they disappear instead and you'll lose out on any loot they might've been carrying.}}
 * Canine Companion: Player characters can optionally start with one depending on their role.
 * Cap:
 * 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.
 * Cheap Gold Coins: A fortune cookie costs 7 gold zorkmids, a food ration costs 45 zorkmids, and artifact weapons cost a few thousand zorkmids. Back-calculation from the weight system suggests that a zorkmid weighs about 40 grams, or about one and a quarter troy ounces. From 2005 to 2015, Real Life gold has varied between approximately $200 and $2000 per troy ounce, so that's $1,750-$17,500 for the fortune cookie, $11,250-$112,500 for the food ration, and a cool million or ten for something like {{spoiler|Excalibur}}.
 * Cherry Tapping: Formerly done to Vlad the Impaler - pre-3.6.1, he was so wimpy that he could be dispatched with a rusted tin opener or thrown magic marker (aptly named "Vladsbane"). Pudding farming pre-3.6.0 invoked this as well, with the farming player deliberately using an iron weapon that inflicts minimal damage to the pudding while still dividing it - this "Puddingbane" allows them to maximize the number of puddings created, and then subsequently killed with an actual weapon, for their death drops and corpses (which can be eaten for intrinsics or sacrificed on an altar).
 * Chess Motifs: Knights have the intrinsic ability to jump to other squares in the same way as the knight chess piece, and unicorns will attempt to keep a knight's jump away from players. Neither can jump through or over other objects, though.
 * Chest Monster: Mimics lurking in stores sometimes disguise as chest-like "strange objects", and are common killers of unwary 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.
 * Purple Is Powerful: Monster kings and other strong creatures often appear with purple glyphs.
 * Combinatorial Explosion: Plenty of items have interesting tandem uses, with some being literally explosive.
 * 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.
 * {{spoiler|Dragon scales (dropped by dragons) enchanted by a scroll of enchant armor become dragon scale mail, one of the best armor choices. Similarly, a wielded worm tooth enchanted by a scroll of enchant weapon becomes a crysknife.}}
 * No matter how funny it would be, never ever {{spoiler|put a Bag of Holding inside another bag of holding}}. For that matter, don't {{spoiler|put a wand of cancellation or a bag of tricks inside one}}, either.
 * Commonplace Rare: Two of the most useful items in the game are... the magic marker and the can of grease. Both are disgustingly uncommon. Grease is mostly valuable because it is rare—its ability to protect your armor from damage is important, but mostly superseded. Magic markers, however, let you write powerful and valuable magic scrolls on junk parchment for a certain amount of charges from the marker, 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.
 * Conservation of Ninjutsu: Oh, you wish. Letting monsters gang up on you is a quick way to end up dead.
 * Contractual Boss Immunity: Played with. Most quest nemeses are immune to stoning, but otherwise their immunities tend to vary, and many can be felled with poisoned weapons or even wands of death. Taken Up to Eleven with the Chromatic Dragon, who has resistance to almost every element and form of magic - as well as reflection!
 * Convection, Schmonvection: Mostly subverted. 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, leaving you to fall in and die as a result. {{spoiler|The Hell branch in previous versions averted this, killing you instantly unless you had fire resistance.}}
 * Cosmetic Award: Of a sort. The announcer bots in many IRC channels tied to public servers often announce significant events of a playthrough - including when the player reaches a certain experience level, completing one of the optional branches, successfully entering and completing their quest, and when they (almost ineviatbly) die or otherwise end the game. The announcements also account for various conducts as well.
 * Crazy Prepared: The player must be this if they want so much as a chance at winning.
 * Critical Existence Failure: Down to one HP? Go ahead and kick a wall. I dare you.
 * Crossover Cosmology: Each role has their own appropriate pantheon.
 * Curse: Some cursed items have their beneficial effects weakened or else exchanged for normally-undesirable effects - though a cunning player can easily turn all but the worst ones to their advantage.
 * Damage Discrimination: Averted - anyone between a thrown missile or a wand shot and their target stands a chance of getting hit. Also, if you wear a ring of conflict, any nearby creatures will start attacking each other.
 * Deader Than Dead: That Auto Revive up there? It doesn't work if you {{spoiler|genocide your own species or class, or get your brain eaten}}. Well, technically it does, but you just die again.
 * Death by Sex: If you're not careful when you initiate an encounter with a foocubus, you may suffer such stupid deaths as: turning to stone because {{spoiler|you were wielding a footrice corpse and had your gloves removed}}; attempting an encounter at level 1 and getting level drained; having monsters around after you're done and left without your armor on...
 * Death of a Thousand Cuts:
 * This is a common method of dealing with early ghosts - they're very hard to hit for many starting characters, but are incredibly slow and deal little damage with their touch attack. Players who don't want to leave them for later can instead kick them to death - successful kicks will do at least 1-2 HP of damage, and eventually you'll have punted them to the afterlife.
 * Attacking a floating eye in melee can result in you suffering one at the hands of whatever happens across your paralyzed form.
 * Death Ray: The wand of death and "finger of death" spell fire these, and anything it hits that isn't immune will immediately expire. Including you.
 * Debug Mode: Or "wizard mode", rather. Useful for demonstrating and clarifying the results of certain interactions on a live basis that you wouldn't be able to (reasonably) explore in a normal game.
 * Demon Lords and Archdevils: Several of them ({{spoiler|Asmodeus, Baalzebub, Juiblex, Orcus, and many others}}) await you in Gehennom.
 * Department of Redundancy Department:
 * Occurs with some of the roles' experience level rank titles, specifically the Knight at Rank 5 (XL 14-17), the Priest at Rank 4 (XL 10-13), the Rogue at Rank 3 (XL 6-9), and the Wizard at Rank 8 (XL 26-29).
 * Depleted Phlebotinum Shells: Garlic appears as an item, and there are various silver weapons and items that do extra damage if used against demons, vampires and werewolves.
 * Detect Evil: Some artifacts can warn the player of particular types of hostiles.
 * Deus Sex Machina: With proper preparation (or, as many like to say, "protection"), consorting with succubi and incubi can permanently raise your level or stats and is generally a great resource.
 * Diagonal Speed Boost: Naturally, as it's a roguelike. The "grid bug conduct" jokingly refers to players who unintentionally ignore diagonal movement (which makes the game a lot harder).
 * Disc One Nuke: In quite a few ways, be it through an early wish or polymorphing.
 * Some players used to regard "Elbereth" as this. Writing Elbereth in the dust with just their fingers can protect the player from almost all early monsters and many later ones. From 3.6.0 on, it was significantly nerfed to the point of causing another break in the base.
 * Due to starting skill levels, 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) and adding damage bonuses from Strength almost guarantees you'll have a long range killer that can tear through the early game by machine-gunning daggers. Rangers can do the same, but have to find the daggers on their own, as well as develop the skill completely from the base level.
 * Charm monster is an invaluable spell for Tourists or Wizards... if you can find the book and have the right armor to cast it reliably. Once you do, it can prove an absolute lifesaver, as not only can you obtain powerful pets such as the people-eating purple worms, but you can also use it to deter especially menacing attackers, such as minotaurs or a freshly-summoned swarm of nasties.
 * Divine Assistance: Coaligned gods reward regular sacrifices and not-too-frequent prayers from their followers (i.e. players) with various boons such as extra Luck, blessings and even rare artifact weapons!
 * Do Not Drop Your Weapon: Averted - you can disarm monsters with a bullwhip, though enemies can do the same - if Magicbane is your only source of magic resistance, and you're disarmed while somebody with a touch of death is around...
 * Eating greasy food or handling a cursed potion of oil can make your character's fingers slippery, causing them to drop their weapon and anything else they wield for a few turns; this can be remedied by using a towel to wipe them clean.
 * 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.
 * Dracula: One of the many bosses.
 * Dual-Wielding: Blessed +7 Grayswandir and a blessed +7 silver saber, yeah baby!
 * Dummied Out: 'Deferred features' include the shimmering dragon and vorpal jabberwock, as well as unique characters like Cerberus and Charon. There was also planned to be an artifact attack that fired magic missiles (similar to Fire and Frost Brand's planned secondary effects) and spellbooks that could summon spheres. Many of these features and monsters appear in NetHack variants.
 * Draconic Demon: Implied with Ixoth, who fits the bill in multiple ways. Ixoth is a red (fire-elemental) dragon that acts as the quest nemesis to the Knight role, not unlike the standard western dragon; he can utilize fire breath and magic, and his default tile depicts him as a Big Red Devil.
 * Dragon Rider: Dragons are a viable steed for the player character to apply a saddle to. Naturally, you'll need some luck to tame one, though you can also polymorph a pet into one or raise it from an egg.
 * Dunce Cap: Appears as an item that immediately autocurses and sticks to your head if you put it on, and fixes your intelligence and wisdom stats to 6. It also shares an appearance with the cornuthaum, which is only useful to Wizards - making it pure (and apt) Schmuck Bait.
 * Dungeon Bypass: Pick-axes can be used to tunnel around enemies and dig a hole through the floor of one dungeon level down to a lower one, 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). Wands of digging can do the job much faster, but have limited charges.
 * Dungeon Shop: As expected in a roguelike. Shops are an important source of items, and can even give clues as to what the items are via price identifying - their appearance is randomized for each game, and use-testing can be a very Bad Idea.
 * Early Game Hell: Depending on the role, but especially if you're new and playing unspoiled. And yes, this applies without potential "gnome with the wand of death" scenarios.
 * Easter Egg: 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.
 * "You pick up the trapper's tongue. But it's kind of slimy, so you put it back down." {{spoiler|Use the 'pick up' key while engulfed by said trapper.}}
 * "That would be an interesting topological exercise." {{spoiler|Attempt to put a bag inside itself.}}
 * Easy Mode Mockery: Heavily downplayed - you can ascend a game in explore and wizard mode, with such ascensions being ineligible for the High Scores list. Public servers disable these modes by default, but they're still valid options for learning the game.
 * Eat the Dog: You can eat domestic cat and dog corpses, though doing so is a Very Bad Idea™ unless you're an orc or a Caveman.
 * Elemental Embodiment: Earth, fire, air and water elementals show up as dungeon inhabitants and enemies; they can also be summoned by other means, much to the chagrin of anyone messing around with sinks, neutral altars or fountains. {{spoiler|Naturally, they cannot be genocided, and appear at near-maximum level all over their respective Elemental Planes.}}
 * Elemental Planes: {{spoiler|Four of them appear as the final levels of the game, with the Astral Plane being the last of them (likely corresponding to the 5th classical element of aether).}}
 * Elite Mook: Many monsters have more powerful "lord" and "king" variants, alongside other general "upgraded" forms, and it's possible for them to level up into these forms.
 * Enemy Chatter: Hostile monsters will threaten you if you #chat to them; hostile demons, angels and priests will utter maledictions (or just straight-up painful quips) while moving around. Your quest nemesis will also greet you with specific dialogue and continue to boast as you fight them.
 * Enemy-Detecting Radar:
 * The spell and potion of monster detection reveals the current location of all monsters on the floor, hostile or otherwise; a blessed potion or high-skilled casting functions as an actual radar that lets you track monsters near you on the same floor for a limited amount of turns.
 * In addition to telepathy (see Psychic Radar), the warning intrinsic reveals the locations of monsters with a high-enough level - though it does not show what they are, instead using a 1-5 scale of "threat assessment" (with a higher number indicating a more dangerous monster). Warning works well in conjunction with telepathy to spot mindless monsters that the latter will not detect.
 * Certain Weapon of X-Slaying artifacts guard you against the "X" monsters in question by revealing their location on the level.
 * Enemy Scan: The wand of probing gives you information on any monster(s) standing in the direction you zap it, as well as revealing the contents of their inventory if applicable. Magicbane can also probe enemies as one of its many effects. The stethoscope can also reveal some information about an adjacent monster, though to a lesser extent and without directly revealing their inventory.
 * Enemy Summoner:
 * Werecreatures can call monsters within their animal form's class for help, and demons are also capable of "gating" in more of their kind when attacking in melee. {{spoiler|As can you if you catch lycanthropy or attain their forms.}}
 * Many high-level spellcasters (including several quest nemeses) can summon strong monsters to surround you when casting in melee range.
 * Any monster can technically become this if they get their hands on a wand or scroll of create monster.
 * Everyone Has Standards:
 * The dungeon's hostile inhabitants will become aware of your presence far quicker if you have the "aggravate monster" quality, which you can get intrinsically by eating domestic cats and dogs or committing cannibalism (unless you're an orc or a Caveman in either case). Offering your pet's corpse on an altar is a great way to piss off whatever god owns it, too.
 * Some peaceful monsters and even humanoid pets will react with fright if you attack another peaceful monster.
 * Do not kill a unicorn of your own alignment, even if chaotic, or you might not live to regret it. {{spoiler|You'll suffer a -5 Luck penalty (plus any additional applicable penalties if they were peaceful) - by itself, this isn't unsurvivable, but it'll take *quite* a while to make up for. Better not try any wishes in the meanwhile!}}
 * Everything's Better with Samurai: Not only can anyone get a katana, but a bunch of items are renamed in Japanese if you play as the Samurai role.
 * Everything's Worse with Bees: Killer bees are a frequent threat, and one that can prove devastating in the early game if a swarm catches you in an open area. Later levels introduce populated "hives" with a queen bee and globs of royal jelly inside.
 * Everything Trying to Kill You: Oh are they ever.
 * Evil-Detecting Dog: Any 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, a leashed pet will whine or act nervous whenever there's a trap nearby.
 * Evil Has a Bad Sense of Humor: Most hostile demons will frequently utter maledictions when battling you, such as the following gems:
 * Evil Tower of Ominousness: Both Vlad and the Wizard can be found in one; the "fake" Wizard's Towers are designed after Rodney's old dwelling from the earliest versions of NetHack. {{spoiler|One of them contains a portal to the real deal.}}
 * Excuse Plot: There is an amulet in this dungeon, and tou need to find it, then return it to your god. Go. The details and quest branch vary quite widely with each class, but ultimately the basic plot progression is the same - essentially by design, given the genre and amount of randomized features. As reliance on a fixed script would ultimately hinder things, this allows the player to organically "develop" their own story simply by playing through the game.
 * Faceless Eye: Floating eyes can paralyze the player if struck, but are rendered harmless if the player cannot see them.
 * Fair Weather Mentor: There's no penalty for starving your pets to death or abandoning them on another floor besides the loss of the pet via death or untaming. Thankfully, domestic pets are at least replaceable - 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: The game provides almost no direct information about how various spells and items work, what dangers some special monsters present, and so on. The intent is for the Oracle and various rumors to be primary sources of information... except that outside of said Oracle (and blessed fortune cookies), the information isn't guaranteed to be accurate.
 * 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. Many NetHack variants assume you have memorized the guide or else have significant experience in the game, and up the difficulty to match.
 * The Random Number God. If he gets angry, you are screwed. Experienced players have demonstrated that most games are winnable, but you also have to be a very experienced player to truly "appreciate" it.
 * Fantastic Fruits and Vegetables: The nameable fruit, called "slime mold" by default.
 * Fast Tunnelling:
 * Can be done via pick-axe or mattock; player dwarves are faster diggers compared to the other playable species, and NPC dwarves will tunnel quickly and busily through the dungeon if they have a pick-axe or mattock. These can also be used to dig through the floor of most levels.
 * The wand of digging is the fastest means of creating tunnels and holes, and is also a useful escape item, being the quickest way to drop past several floors at once. Speedruns use this strategy when they have places to be - relying primarily and extensively on it is usually called "digging for victory".
 * Rock moles and umber hulks are incredibly quick diggers and can literally chew their way through the dungeon walls, as can you if you take their forms.
 * 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 outside of wizard or explore mode, unless you have a certain rare item...
 * Fire and Brimstone Hell: The Valley of the Dead and Gehennom (formerly known as just Hell).
 * Fish Out of Water: Humans are implied to be this for the Dungeons of Doom, according to the encyclopedia entries.
 * Foe-Tossing Charge: The game has many potential instances where the player is surrounded by monsters and only needs to pass through; the easier way to do this (or something resembling this) is zapping a wand of teleport through the horde, or else breaking a spare one in two and teleporting anything within range. In games where the mail option is enabled, the mail demon (no, not this kind, an actual demon) will do this if necessary in order to get to the player and deliver their message. {{spoiler|The Riders can also shove monsters out of the way to get at you on the Astral Plane.}}
 * Forgot to Feed the Monster: While food is very common and you usually don't have to actively feed your pet(s), it is possible for them to starve to death. This can annoyingly be reversed if you're hungry, but your pet gets to corpses and other edible food before you can. Pets that become extremely hungry will be confused and may end up attacking you until the come to their senses. Your pet(s) can also untame or even go feral if you leave them on a different level for too long; in the case of domestic pets, feeding them will re-tame them. This trope is averted for pets that are inediate - they do not need food and thus cannot starve, though tameness mechanics still apply.
 * 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.
 * Frankenstein's Monster: Flesh golems are modeled after him - they resist shock damage and are healed by it, and their encyclopedia entry directly quotes Mary Shelley's Frankenstein.
 * Friendly Fireproof: Averted. Ranged attacks from any source can hit anything in the line of fire, including other peaceful or hostile monsters.
 * From Nobody to Nightmare: Vlad the Impaler in 3.6.1 - he went from the butt of every player's jokes to the second-fastest monster in the game and a level-draining menace.
 * Full-Frontal Assault: The default tiles for foocubi.
 * 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 Libera.chat IRC channel after their death, and GwtWOD (The Gnome with the Wand of Death) which is a disappointingly common cause of YAAD.
 * The archived FAQ from the Usenet newsgroup is a good source of these and many more such acronyms that are still in use.
 * Game Mod: The NetHack General Public License encourages the creation of patches, variants and other similar additions - this category contains many of the variants available.
 * Gender Bender: Possible through polymorphing or with amulets of change (which are usually cursed).
 * Genie in a Bottle: In magic lamps, as well as actual bottles. {{spoiler|(Specifically smoky potions.)}} They're a possible source of a wish if handled correctly.
 * Genius Bruiser: Players inevitably tend towards this style of play to varying degress as they progress - in NetHack, picking your battles wisely and having creative solutions for disposing of baddies is 80% of the final grade.
 * "Get Back Here!" Boss: Quest nemeses, end-game bosses and other powerful enemies can warp at will, and will use this ability to run off and heal. {{spoiler|Generally speaking, they always warp to the stairs leading to the previous floor, meaning once they start that nonsense, you should be running that way, too... or preempt them by blocking the stairs before facing them.}}
 * Gods Need Prayer Badly: Inverted - your god will be cross with you if you call on them too much. {{spoiler|Yeenoghu is a notable aversion, as his encyclopedia entry explicitly states that his followers were wiped out.}}
 * Golem: Various types serve as enemies; they are notable for being impossible to genocide, and can result from polymorphing piles of like items.
 * Gone Horribly Right:
 * Killing monsters and gaining levels too fast will eventually generate foes that are out of your league if you lack adequate weapons and/or armor.
 * With work, it's possible to genocide a whole range of weaker creatures - but overdo the blessed scrolls of genocide and all that's left are the ungenocidable creatures, among which are some of the very toughest enemies you'll face. This makes the final stages of the game even more exciting, and frequently much shorter, too.
 * Good Hurts Evil: Undead and demons take bonus damage from blessed weapons.
 * Good Is Not Nice: Oh, angelic monsters such as Archons and ki-rin can be plenty nice most times if you're lawful - but if they're hostile towards you, you're in for it.
 * Gratuitous Japanese: When playing a samurai, the game feedback will call certain items by their Japanese name (helmet -> kabuto) or a rough Japanese equivalent (booze -> sake), though they're ultimately the same item besides. The Samurai Quest is particularly full of this.
 * Grave Humor: Many a randomly generated grave (i.e., not created by a player's death) comes with a humorous message. The server run on nethack.alt.org adds a ton of them.
 * Grave Robbing: You can dig up graves to find gold and items, though you may also unearth mummies and zombies, and the loot may be cursed as well. Lawful roles, including Samurai and Archaeologists in particular, suffer alignment penalties if they engage in this.
 * Griping About Gremlins: NetHack gremlins are chaotic, Gizmo-like creatures.
 * Guardian Angel: {{spoiler|If you have good enough alignment upon entering the Astral Plane and are not generating conflict at any point after, a tame one will be sent to assist you.}}
 * Hailfire Peaks: The Valkyrie quest's home level has both lava and fire traps littering the naturally-icy area, 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. 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.
 * Healing Hands: There's an entire school of healing spells, and enemy casters can usually heal themselves with their magic.
 * Highly-Visible Ninja: Ninjas only appear on the Samurai quest, and aren't intrinsically capable of most the usual tricks associated with ninja. They do come with some of the Stock Ninja Weaponry, though.
 * Hoist by Their Own Petard: The easiest way to kill Medusa is with {{spoiler|her own reflection. This includes any item that provides reflection}}.
 * 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 base Luck stat 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 10pm and 6am, some creatures are slightly more dangerous.
 * From midnight till 1am, undead do twice as much damage, and you get a different message when entering graveyards.
 * Hollywood Acid: Averted in that most acid attacks cause relatively lower damage and corrodes metal items, instead of instantly dissolving them or their target.
 * Holy Burns Evil: Werecreatures, vampires, and demons are weak to silver.
 * Horny Devils: Foocubi (the gender-neutral name used for the succubus and incubus) can seduce the character (or just about anything of the opposite sex, including a dragon steed), cause a random effect (positive or negative depending on stats and chance) and teleport away.
 * Horsemen of the Apocalypse: {{spoiler|Death, Pestilence, and Famine (referred to as The Riders) make an appearance as optional end bosses in the Astral Plane. War is the player.}}
 * HP to One: The player can do this to certain monsters. {{spoiler|Specifically, if you're being engulfed by something solid, zapping a wand of digging through them will reduce them to 1 HP and force them to expel you.}}
 * Human Sacrifice: Same-species sacrifice is possible, but highly unadvisable unless you're chaotic.
 * I Fought the Law and the Law Won: Keystone Kops spawn in large numbers if you rob a store, even by accident. Downplayed in that you can fight and defeat them, though it may be less tedious or dangerous to just pay up: they are also among the only monsters in the game that can never be rendered permanently extinct, so 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. Even when you're high level and well-tooled for melee with AC well in the negatives and a ring of regeneration, and you can smite an entire room of trolls and dragons, taking blows and regenerating the damage faster than they can dish it out, you can still get absolutely destroyed without the proper resistances, and in some cases even with them!
 * Improvised Weapon: You can wield nearly any item and use it for the blunt-force trauma if nothing else.
 * Infinity+1 Sword: Grayswandir is a silver saber which deals double damage to all monsters (instead of just extra damage like other artifacts), plus the usual extra damage to silver-hating monsters. It's widely considered the best artifact in the game, and as a double-damage silver saber is most ideal for carving through Gehennom, to the point that even non-Lawfuls may choose to wish for it in the late game - it's not intelligent and won't evade their grasp, and the "cross-aligned" artifact blast only does 4d4 damage.
 * Ranged attacks that make use of a multi-shot weapon at skilled level or better can kill enemies before they even get withing melee range (typically called "storm" damage).
 * Cone of cold and fireball cast at skilled or better level can created repeated area-of-effect explosions that rack up tons of damage.
 * Magic Missile in the hands of a Wizard or other sufficiently-powerful caster will make short work of nearly anything without reflection, up to and including the final bosses.
 * I'm a Humanitarian: Eating your own species is possible, but in most scenarios it's also a Very Bad Idea™.
 * Interface Screw:
 * The Rogue level can be confusing to navigate if you're new or used to playing with tilesets, as it uses the GUI of the actual game.
 * Some of the Standard Status Effects can prove horrendous. When confused or stunned, moving takes you in the wrong direction most of the time; when hallucinating, you can't tell friend from foe. When blinded, you can't see anything, and unless you have a means of telepathy, you risk bumping into or touching something that may turn lethal in short order. Better not get blinded in shops and towns!
 * Inventory Management Puzzle: For sufficiently advanced and/or paranoid players, most of the difficulty (and/or tedium) will come from this. You can carry a lot of swag with the right items, but eventually you'll have to start stashing; to be as certain as possible of not losing a cache, you can {{spoiler|put it in a pit and push a boulder on top of it}} or {{spoiler|put it in a (preferably locked) chest, on a scroll of scare monster, on a dungeon tile which has "Elbereth" engraved on 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: Available through a cloak and a ring, as well as intrinsic invisibility conferred by wand (permanent), potion or spell (temporary). Note that it doesn't make you completely undetectable; monsters will try to guess your location and attack where they think you are, and some monsters can see invisible creatures outright. All of the above items can also be used by monsters, making the "see invisible" intrinsic important.
 * Invisible Monsters: In addition to the above being available to monsters, the stalker is a form of elemental that is naturally invisible at all times. Eating one can provide a source of invisibility and the ability to see other invisible beings. {{spoiler|The method its corpse provides you with the latter will also turn you invisible indefinitely, however.}}
 * Just Add Water: Several types. For example, alchemy can be used to mix potions and generate more-useful ones.
 * Katanas Are Just Better: They use the same skill as the long sword, but have slightly higher damage against small monsters and are +1 to hit. Snickersnee is an artifact katana that serves as the first sacrifice gift for Samurai.
 * Kick the Dog: You can do this if you like, even literally. You Bastard. Seeing as your pet is your loving sidekick and one of your more useful assets, this is usually an accident when it happens. {{spoiler|On occasion, you may have to go so far as to Shoot the Dog if it turns on you. Offering your pet on an altar makes that altar's god angry at you, by the way.}}
 * Killer Gorilla: Apes are a semi-frequent occurrence in the Dungeons of Doom, alongside carnivorous apes and owlbears; all these and other monsters share the  glyph, used to represent apelike creatures. You can at least tame regular apes with bananas.
 * King Mook: Gnome kings, dwarf kings, ogre king, Elvenkings, and queen bees. They are the strongest of their respective monster classes, and can even appear in throne rooms occupying the square with the throne - except for queen bees, which appear in beehives instead.
 * Monster Lord: "Lord" variants of the above monsters (minus bees) appear as well, and can grow up into their respective "king" forms.
 * Both monster lords and monster kings get a +1 bonus to multishot for projectile weapons and tend to generate with better quality equipment. Monster kings also get two attacks per turn.
 * Kitchen Sink Included: With a surprisingly large number of gameplay uses.
 * Late Arrival Spoiler: Part and parcel with a game that's been active since 1987.
 * Leaning on the Fourth Wall: Applying a stethoscope to listen to the very bottom of the screen gives the message "You hear a faint typing noise."
 * Level Drain: Life Drain abilities tend to double as this, particularly when used by players. A player hit with a level drain is left at the minimum experience required to regain that level - better not get-double tapped! Wraith-type monsters are also capable of draining levels with their touch attacks - interestingly, standard wraiths can leave corpses that act as a Rare Candy and may increase your experience level by one. In addition, lost levels can be partially or completely restored through prayer, potions of full healing, or potions of restore ability.
 * Level Grinding: Possible, but depending on the scenario it's not always recommended.
 * Priests and Wizards have quest branches that can generate a lot of wraiths, whose corpses can be eaten to gain an experience level.
 * The "pudding farming" method allowed you to collect massive amounts of hit points, as well as really good loot, at the cost of turning the remainder of the game into a tedious slog. Prior to the release of 3.6.0, a player joked that the Dev Team didn't need to invent a punishment for pudding farming because there already was one—{{spoiler|"it's called pudding farming."}}
 * Anti-Grinding: Leveling up too much before you find good equipment is a good way to get yourself into trouble, especially against monsters with better AC such as giant ants.
 * Level Scaling: The level of enemies you'll face is based on the average of your character level and the depth you've reached in the dungeon. In theory, this discourages players from diving too deep too fast.
 * Beef Gate: In practice, however, this is still quite survivable, especially for experienced conduct players. NetHack as a whole is generally approached as a test of wits as much as it is one of fighting strength.
 * Life Drain: Appears as an attack spell and an ability used by monsters such as vampires and foocubi. The Healer quest artifact can also drain the life of its targets, and {{spoiler|Stormbringer}} is capable of doing the same.
 * Logical Weakness: Tridents do additional damage to aquatic monsters that are swimming; axes do extra damage to wood golems; and clay golems can be destroyed in one shot if you've read the original folk tale {{spoiler|and know how to erase the runes on their foreheads}}. The list goes on...
 * Luck-Based Mission:
 * Luck (both in the sense of the stat and RNG) 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. 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 from wandering into one; the truly paranoid will try to only step where they've seen other monsters step safely, or search when that's not possible.
 * 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 role for the first 13, prior to doing conducts.
 * Adeon, another NAO player, ascended 29 times in a row over the course of just barely more than one month.
 * Luck Stat: Exists in the game and is affected by circumstances such as moon phase, date, and other factors, e.g. Friday the 13th naturally results in lower base Luck.
 * Luck Manipulation Mechanic: Your capital-L Luck can be raised and lowered through various actions, ranging from the standard (gaining Luck by sacrificing to your god or losing Luck by breaking a mirror) to the unusual and frankly absurd (losing 1 point of Luck for hitting a blind floating eye ). {{spoiler|Luck normally times out by 1 point every 600th turn of the game - having a noncursed luck item such as a luckstone boosts your Luck and partially or completely prevents it from timing out.}}
 * MacGuffin: The Amulet of Yendor is the primary one, and each role also has a quest artifact specific to them, guarded by their quest nemesis. Said nemesis, Vlad the Impaler, and the Wizard of Yendor also guard the three items needed to access the Amulet of Yendor.
 * Macrogame/Metagame:
 * Bones files add another dimension to playing NetHack when on an online server (or playing locally and using Hearse). These allow you to possibly stumble upon the "bones" of your previous characters and others, loading the floor in question as it was at their time of death instead of creating a new level. The good news is that you can take whatever items they left behind once you deal with their ghost - the bad news is that whatever killed them might still be around...
 * Many sort-of-intentional deaths are caused on the first few levels by people repeatedly seeking some early advantage: quaffing from fountains (as "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 or 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.
 * In regards to intentional deaths, some players have used it as a form of griefing by intentionally luring or creating powerful monsters to reasonably early levels, then dying to them in the hopes of creating an "impossible" bones file that stonewalls other players. Measures have been taken to prevent this on servers.
 * A somewhat more benign use of bones involves "stuffing" - creating as many bones as possible on a given level, or else "stuffing" a single bones files with as much ideal loot as possible, all in the hopes of coming across them with another character. Doing this on purpose is still considered bad form, with the exception of specialized speedruns.
 * Mad Oracle: Downplayed with the Oracle of Delphi, who is always guaranteed to appear in every game (barring bones shenanigans). She can be paid for consultations, which is one of the main ways an unspoiled player can learn about the game - where the "Mad" aspect comes in is that some of her consultations, while cheap and always true, are a bit on the obtuse side. While on her level, you can also occasionally hear "conclusive ravings".
 * Magic Mirror: Appears as one of many quest artifacts.
 * Magic Missile: One of the many spells available in the game, and can become ridiculously powerful due to scaling with your level. Other monsters such as Angels and the Oracle also have this as a natural ability, as does {{spoiler|the demon lord Yeenoghu}}.
 * Magic Pants: Despite the amount of slots available, there are no mention of pants in the game whatsoever. If you sit on a cockatrice corpse, however, you don't turn to stone, so you must be wearing pants. Since they don't tear apart or anything, the pants are thus present and magic - it's the rest of your armor that's endangered if you polymorph. Change into a much larger form and the body armor you're wearing will be torn apart and destroyed; turn into something exceptionally small, and you'll be half-squashed by the same armor while finding it harder (if not impossible) to move.
 * Magic Wand: Wands can be found in the dungeon that have various magical effects, ranging from offensive rays to self-buffs to utility effects.
 * Magikarp Power/Lethal Joke Character: Arguably all the "weak" roles 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 usually a big "if".
 * Throwing darts are weak, but light and prove sufficient for most roles as a ranged attack even if they lack the related skill; there are also plenty of dart traps to un-trap for more darts. {{Spoiler|Poison them with a potion of sickness and they can be a big help.}}
 * 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.
 * Mana: Replaces the Vancian Magic system as of 3.3.0, though you still have to learn and re-memorize spells to be able to cast them.
 * 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: Appears as a boss on her own unique level which has elements that allude to her myth, such as a statue of Perseus.
 * Meta Multiplayer:
 * Nethack tracks the top 1000 player scores, which can be seen by other players on the same system (e.g., a public server), and "bones files" that store the contents of a level on which a character died may be loaded in lieu of normal level generation. The program Hearse can be used to exchange bones files with other players when playing outside servers (which store bones for use in other games by default).
 * Public servers also have specialized bots that print text for significant in-game events; for example, NAO's Rodney announces ended games (i.e. deaths, escapes and ascensions), and Hardfought's Beholder announces other significant events - such as when a player has completed a branch, picked up a notable item, killed a noteworthy enemy, or commits certain conduct-breaking actions.
 * Metasyntactic Variable: "Foo" is a loanword from hacker jargon often used in discussion of NetHack, typically involving sets of creatures with similar characteristics (e.g. foocubi and werefoo).
 * Mighty Glacier: Many quadrupeds qualify as this.
 * Rothes are an early game example that move somewhat slow, but get 3 attacks per turn, and often generate in herds. They are usually among the earliest instances where a player will have to employ crowd control and kiting to avoid being battered to death.
 * Mumakil and baluchitheria. The mumak is somewhat slow but hard to hit, and possesses a headbutt attack with the highest possible hit die in the game; the balucitherium is slightly faster and tougher, but has less AC, though it can still do solid amounts of damage.
 * The wumpus is extremely slow and often generates asleep, but its sole bite attack can deal solid damage.
 * Minigame Zone:
 * The Sokoban branch uses the same mechanics as the rest of the game, with only minimal changes to the adapted Sokoban mechanics themselves; boulders can't be pushed diagonally as usual, but you also can't fly over the pits and holes in the floor, and certain actions (e.g. making or removing boulders) will incur a Luck penalty.
 * One way to enter the Castle is to invoke this by winning a game of Master Mind.
 * In the endgame, {{spoiler|wielding the Amulet of Yendor lets you play hot/cold to find the hidden portals to the next level.}}
 * Mission from God: The core of the Excuse Plot.
 * Money for Nothing: There are some things 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 and items, you're more or less done with money as well - unless you plan to try Bribing Your Way to Victory against some of the demon lords you'll meet.
 * Monsters Everywhere: Horses, bees, trolls, elves, snakes, demons - and everything in between. They seem to just grow out of the 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, fighting side by side!
 * Mook Bouncer: The quantum mechanic has a teleport attack, which is based on its Punny Name along with many of its other elements, and sends you to a random spot on the same floor. {{spoiler|Angering your quest leader or killing any guardians will get you ejected from that branch, in most cases permanently.}}
 * Mounted Combat: Possible with any role as long as you have a saddle and a compatible steed to apply it to, though only certain roles can actually level up the riding skill.
 * Powerup Mount: While riding, your movement speed is set to that of your steed, and your carrying capacity is maxed out; polearms can be used more effectively at close range while riding. In addition, flying mounts can carry you over water, and you don't have to worry about falling off one by traveling downstairs unless you're burdened. However, you cannot eat food (notably corpses) off the ground while riding, and can only pick up items off the ground with at least Basic riding skill. Monster attacks may also fall upon your steed instead of you - better hope a footrice attack doesn't go astray! You also can't enter shops while mounted.
 * Multi-Armed and Dangerous: Mariliths. While they can't actually wield more than two weapons, they still get several "claw" attacks per turn.
 * Multiple Head Case: Ettins are two-headed distant relatives to giants that get two attacks instead of one, and can ignore player stealth a majority of the time. Also the case with {{spoiler|Demogorgon}}.
 * Mundane Utility:
 * Basic leather gloves do nothing for you besides covering your hands and providing extra AC. But even that is enough for the mid-game and on: {{spoiler|Having any form of gloves lets you wield cockatrice corpses safely, and they can be enchanted to provide even more AC.}}
 * Simple sacks let you carry objects within them, which can also protect them from some types of damage and allows you to carry more than the 52-character limit. {{spoiler|It can also hold bags of tricks and wands of cancellation that would explode a Bag of Holding if placed inside one.}}
 * Mushroom Samba: The hallucination effect can be obtained by drinking a certain type of potion, eating the corpses of monsters with stun attacks (including some fungi), and being hit by an exploding (and usually invisible) black light. This causes nearby monsters and items to appear as random other items or monsters that may not actually even exist, and also gives alternate messages for some other effects.
 * Needle in a Stack of Needles: One of the things the Wizard of Yendor can do to make your life more difficult is steal the Amulet of Yendor and then leave a fake behind. Do not try to enter the endgame without the real one... {{spoiler|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, they just "feel uneasy" and nothing happens; if they do have the real Amulet, it's up and out into the Planes.}}
 * Nerf Arm: Cream pies are surprisingly useful as weapons - and you can eat them.
 * Nintendo Hard: To the point that 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. It's not unheard of for players to die on their first turn, though that's far more due to extremely bad luck or deliberate actions than a lack of skill.
 * No Body Left Behind:
 * Some monsters are coded to never leave corpses for various reasons, from lacking a physical body to having one that dissipates upon death (e.g. liches crumble to dust).
 * This can happen to most other monsters - including you - that are caught in the path of a disintegration blast and lack reflection or resistance.
 * Nobody Poops: No matter how much food you or your pet consume, you'll never feel unpleasantly "backed up", though you do risk choking if you eat while oversatiated. There's no toilets in the dungeon anyway. Although there are sinks. See also Bottomless Bladder above.
 * No Fair Cheating: Attempting to alter a save file will usually trigger a dungeon collapse, immediately ending the game (with the cause listed as "death by trickery").
 * No Hero Discount: Played with - you can actually get a discount off base prices if your Charisma is high enough. The Healer and Tourist, the only roles that start with any gold, have stats that slant in favor of high Charisma, as does the Knight.
 * Inversely, being seen with a T-shirt or Hawaiian shirt (or wearing a dunce cap) will cause shopkeepers to hike their rates by at least 1/3 (non-cumulative). Naturally, the Tourist role starts with this, and are also subjected to this below a certain experience level, though their potential for high Charisma can mitigate this.
 * Non-Human Undead: Zombie and mummy giants, elves, dwarves, orcs, and gnomes can be found along with the regular ol' human variant.
 * No Ontological Inertia: Once you clear a Sokoban level, the movement restrictions regarding boulders are lifted, as are the penalties for breaking boulders.

{{quote|{{spoiler| }}}}
 * 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).
 * Not the Fall That Kills You: Subverted - falling into a pit (or {{spoiler|falling into a sink while floating above it}}) will damage and even kill you, especially if there's spikes involed. Falling through a hole or trap door, on the other hand, has you land harmlessly on a lower floor, and can be used to drop past several floors - but beware of more difficult monsters.
 * The Nudifier: Any piece of armor can be destroyed via the scroll of destroy armor and the 'destroy armor' spell used by certain monsters.
 * One-Hit Kill: Tons of 'em, on both sides.
 * A wand of death, the finger of death, a bad roll on a poison check with no resistance, anything involving your bare skin and anything even tangentially related to a footrice or their eggs, Medusa's gaze...
 * Other situations can be "effective" one-hit kills, such as hitting a floating eye (which leaves you paralyzed and helpless for several turns, meaning anything can get free shots at you) or encountering anything from a soldier ant (Go Team a!) to monsters like the leocrotta, mumak and minotaurs when completely unprepared for melee.
 * Drowning attacks are technically a two-hit kill, but feel like a one-hit kill; if a monster is already securely wrapped around you near water and lands the grabbing attack again, it instantly pulls you in and drowns you.
 * Optional Sexual Encounter: Succubi and incubi - the page image for that trope is from this game.
 * Orcus on His Throne: Various monsters such as King Mooks and Croesus can be found "asleep" on thrones in special throne rooms. {{spoiler|Croesus's alarm system will immediately wake him up, however. The Trope Namer himself appears, but is an exception to the rule - he "meditates" while awaiting you on the down stair of his lair instead, and will spring to action immediately once aware of your presence.}}
 * Our Demons Are Different: Demons tend to appear primarily in graveyards, the Valley of the Dead and Gehennom, and they are immune to fire, poison, death rays and Level Drains.
 * Our Dragons Are Different: NetHack dragons are of the quadrupedal variety; they are intelligent and can pick up items, but lack "hands" to actually use them with, and each type has their own breath weapon that they generally use at a distance. They tend to appear in late-dungeon throne rooms, as well as near and within castles, and are "nasties" that can be summoned by enemy spellcasters. Ixoth and the Chromatic Dragon respectively serve as quest bosses for the Knight and Caveman.
 * Our Ghosts Are Different: Ghosts occur in graveyards and abandoned temples, and in most cases where a player's death leaves a bones file, you can find the character's ghost near their belongings, along with any pets they had - as well as whatever killed them. While ghosts themselves are not all that damaging, they can prove very hard to hit due to their AC.
 * Our Giants Are Bigger: Giants can't wear torso armor, but can somehow still use other armor and weapons, and their strength lets them carry boulders with ease.
 * Our Werebeasts Are Different: Werewolves, wererats, and werejackals exist, and each of them can call their 'fellow' beasts for help.
 * Palette Swap: The standard game is constructed entirely of ASCII characters, leading to a lot of creature-overlap both in cases of Underground Monkey (e.g. wolves and winter wolves) and otherwise. You definitely still don't want to confuse a dwarf king with a mind flayer (both are a purple {{color|purple|h}}). Or a Mordor orc with a floating eye (one a dark blue {{color|darkblue|o}}, one a dark blue {{color|darkblue|e}}.) Various alternate tilesets can be used to supply more information.
 * Underground Monkey: As a more traditional example, some monsters have elemental variants that are at least resistant to their element's damage (e.g., fire giants and frost giants), and eating their corpse may confer that resistance.
 * Pet Interface: There's a surprising amount of mechanics and options for taming monsters:
 * The 'safe_pet' and 'highlight pet' options.
 * Carrying pet treats in open inventory (e.g. 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 call your pet's attention to you. A magic whistle will teleport your pet(s) to your side from 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, and can also be used to control their movement.
 * You can apply a bullwhip at a humanoid pet to take their weapon, then leave a better weapon for them to replace it with. You can also prepare and leave weapons, armor, and tools for your humanoid pets to pick up and use.
 * A wand of probing tells what a monster (tame or otherwise) is carrying; a stethoscope displays a monster's basic Hit Points and its speed.
 * Spells of healing and extra healing can be used to heal pets, as can breaking a potion of regular, extra, or full healing on them.
 * Saddles permit horses, dragons, and some other monsters to be ridden.
 * Olympus Mons: Figurines, the spell of charm monster and the scroll of taming make this possible. 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 {{spoiler|two of the Horsemen of the Apocalypse}} can be brought under your control.
 * Pinball Projectile: Rays from spells and wands can be bounced off walls to hit tricky targets. They might also bounce back at you.
 * Plague of Locusts: Several variants - among them SporkHack, UnNetHack, EvilHack, and SlashTHEM - have the locust as an enemy monster which often appears in swarms and is capable of inflicting terminal illness on players, bringing down even the most seasoned of combat veterans unless they can avoid/cure the sickness and defeat the swarm quickly.
 * Plot Coupon That Does Something: The items used for the invocation can also be used for other purposes, and can even be a handy substitute for other parts of a kit. {{spoiler|For example, the Bell of Opening works as an area-of-effect wand of opening, which you can use to enter the Castle, and can double as a silver weapon to hit the shades in Orcus Town with. The Candelabrum of Invocation can be used as an alternative light source, though this is usually reserved for Astral Plane jumping. And finally, the Book of the Dead can raise the dead, and chaotic Priests can use this with Turn Undead to obtain a horde of tamed monsters.}}
 * Portal Door: You're guaranteed to encounter at least a few of them, including the one leading to your quest. {{spoiler|Another is necessary to reach the Wizard of Yendor, and the Elemental Planes past the Plane of Earth can only be reached via a portal you have to find in each one.}}
 * Press Start to Game Over: If you're very unlucky with the Randomly Generated Levels, or else going out of your way, it's possible to die on your first turn, and there's even a special Have a Nice Death message for it; ais523 proved that this is indeed possible before you even have control of your character. {{spoiler|Grayswandir was generated on the upstairs; the neutral-aligned player character picked it up due to autopickup, and the lawful artifact blasted them to death.}} He did some calculations and estimated a 1 in 3 million chance (roughly) of this occurring.
 * Psychic Radar: When blinded, telepaths can see any non-mindless monster on the current floor; extrinsic telepathy additionally lets you see the ones closer to you when not blinded.
 * Psycho Electric Eel: Watery areas and swamps can generate them, and they're a major hazard that can destroy rings and wands.
 * Public Domain Artifacts: Several of them can appear in the game: The Hobbit universe's Orcrist and Sting, Snickersnee from The Mikado, King Arthur's sword Excalibur, Thor's trademark weapon Mjollnir, and the tsurugi of Muramasa. There's also Stormbringer of The Elric Saga, and Grayswandir from Roger Zelazny's Book of Amber, which technically won't be public domain for another 80 years yet.
 * Public Domain Characters: Vlad the Impaler and the various deities, among others such as Classical Mythology figures like Medusa and the Oracle of Delphi. Cerberus and Charon are Dummied Out examples.
 * The Quest: There's one for every role that takes them back to their home land, with their leader assigning them to retrieve a special artifact from a unique boss monster, or "quest nemesis" (thus doubling as a Fetch Quest). Said nemesis also has one of the three Plot Coupons needed to complete the game.
 * Randomly Generated Levels: Most of the dungeon floors in NetHack are created the second you enter them - the exceptions include non-filler Quest levels, the Castle, and any floor that bones occur on. Levels that are not randomly generated but have no set appearance (e.g., Mines' End, Sokoban, and Medusa's island), are instead created by choosing a layout from a set of templates. There are also levels that will always have certain fixtures within them while randomly generating the rest of the level around it.
 * Rare Candy: Potions of gain level and wraith corpses give level-ups, and potions of gain ability (especially blessed) and the "gain ability" effect of magic fountains increase stats.
 * Reality Ensues: Since The Dev Team Thinks of Everything, a lot of interactions (and the deaths that can result from them) are surprisingly logical, and often distressingly so.
 * Regenerating Health: All monsters can regenerate health gradually outside of combat, including the player; in the latter case, it's subject to how encumbered you are. A ring of regeneration can improve regeneration rates at the cost of lowering your nutrition faster, and the Healer quest artifact provides this perk without the latter downside. Werecreatures and trolls are monsters that boast impressive heightened regeneration.
 * Religion Is Magic:
 * Donating to temple priests (of any stripe, not just ones serving your god) can grant you additional favors such as bonus AC and alignment. Co-aligned temples can additionally serve as sanctuary, causing non-angelic hostiles to flee from you.
 * The Priest role has an innate Aura Vision-like ability to tell the beatitude of objects without the need for identification or an altar.
 * A special form of Turn Undead is available to the Knight and Priest roles, and using it can scare or even destroy nearby undead. Be careful, as using it will leave you helpless for some turns.
 * Required Secondary Powers:
 * Scrolls of fire and books of fireball can't burn; wands and books of cancellation can't be cancelled; wands, potions, and books of polymorph can't be polymorphed, and wands of lightning cannot be destroyed by shock damage.
 * Receiving an artifact weapon as a gift from your god will unrestrict the corresponding weapon skill if it is not available, allowing you to attain at least Basic skill with that weapon. Certain artifacts also have secondary effects tied to their element (e.g., Fire Brand and Frost Brand provide fire and cold resistance respectively while wielded).
 * Resurrective Immortality: Trolls will continually revive from their corpses unless they are killed in a way that doesn't leave a body, or else if the corpses are stored or disposed of. {{spoiler|This is also true of the Riders on the Astral Plane, who additionally cannot be eaten or tinned and are too heavy to lift.}}
 * The Wizard of Yendor can revive as well and will do so an endless amount of times, no matter how you actually kill him. {{spoiler|He can harass you remotely even while dead, and once he does revive, he'll immediately appear in front of you to continue the fight. He's guaranteed to resurrect or reappear at least once on the Plane of Earth, and will harass you this way until you make it to the Astral Plane.}}
 * Ret-Gone: A scroll of genocide not only kills all monsters of a given type, it removes them from the current game and prevents them from generating in any other way. If you genocide cockatrices and you were holding a cockatrice corpse 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 becomes empty. And you'll find yourself unable to polymorph into the genocided form now, even if you had already done so before.
 * {{spoiler|Also, if you genocide your own base species or role while polymorphed, the game will say "You feel empty inside", and you will die if you turn back; if you quit anytime afterward, the death message will read "quit while already on Charon's boat."}}
 * Robe and Wizard Hat: Appear as items in the game. The Wizard role starts with a cloak of magic resistance, and is the only role that can reap benefits from the trademark pointy hat (called a "cornuthaum"). A more "traditional" robe that improves spellcasting success is also one of the many cloaks available, and both Monks and Priests start the game with one.
 * Rodents of Unusual Size: Giant rats and rabid rats are common early-game enemies, and the ROUS is one of the many hallucinatory monsters.
 * Rogue: The predecessor of NetHack has a Shout-Out level dedicated to it that adapts some of its rules.
 * Rule of Three: There are three alignments, with a god to each alignment, and there are three end game bosses to fight for the three items needed to obtain the Amulet of Yendor. {{spoiler|You also face the other three Horsemen of the Apocalypse as War, the fourth Horseman.}} Erinyes are monsters that you can only ever meet three of in a given game.
 * Save Game Limits: The game only allows one savefile per character in the standard mode. 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.
 * The "explore" and "wizard" modes are an exception that allow you to keep an old save file - in normal play, once a saved game is restored, the file used to hold the saved data is deleted. In explore and wizard mode, once restoration is accomplished you are asked whether to keep or delete the file, and keeping it lets you quit without saving and later restore it again (which can be used troubleshoot and test multiple outcomes from a given scenario, for example).
 * Save Scumming: Like just about any roguelike, NetHack only allows one savefile per character, removes a save upon restoring it and erases your save upon death; as explained above, it is still possible to do, but heavily discouraged unless there's an actual purpose to it.
 * Some players will do the inverse and "start scum", repeatedly starting and quitting the game until they get a favorable set of starting equipment or stats. This is usually done with wizards, due to the ridiculous (and pre-identified!) magical items a lucky wizard can start the game with. A little over 50% of all NAO games are turn-0 quits, and a good portion of those are wizards. Whether or not it's acceptable depends on the circumstances - for what it's worth, even the best start in the world won't matter if the player is subsequently terrible or else just plain unlucky afterward.
 * Schizophrenic Difficulty: Despite dangers like arch-liches, mindflayers, and {{spoiler|Rodney chasing you}}, the game can feel much, much easier after the first dozen levels or so due to the necessity of being Crazy Prepared for early monsters considered to be vastly overpowered, such as soldier ants, leocrottas, and chameleons. As you learn the tactics required to handle these early threats, you also adapt them to later ones, and the game also remains difficult enough that the aforementioned dangers can still throw you for a loop.
 * Schmuck Bait: The community refers to tactics that are very likely to kill the player as Bad Ideas™. Using and trying on unidentified items randomly qualifies as this, since many such items have at least one type designed to punish this type of thoughtlessness (e.g. rings of hunger, amulets of strangulation, scrolls of amnesia). Go ahead, try that scroll labeled READ ME and see what happens. Wearable "gotcha" items will also often generate as cursed for added insult to injury.
 * Sdrawkcab Name: Yendor. The Wizard of Yendor is affectionately referred to as Rodney as a consequence (which is Yendor backwards). The origin is part-J. R. R. Tolkien inspiration and part Rogue allusion (Rodney is the default name of its player character), among a few other possible sources.
 * Sealed Room in the Middle of Nowhere:
 * Vaults can be found on random levels and accessed by digging to them or teleporting there, which can happen by accident. A guard comes along to check it occasionally, and can even help you escape if you have no other means to (though you'll have to drop your gold first). However, you can fool them through a few means.
 * The Rogue quest's goal level consists of these, and unlike vaults you can't dig into them through the walls, forcing you to find another way to get at the quest nemesis.
 * Self-Imposed Challenge: Formally known as "conducts", NetHack's randomization allows for a lot of them; the distinction between an "official" and "unofficial" conduct is whether or not the game actively keeps track of how you adhere to it. The game also has options that can alter the starting character to fit the desired conduct.
 * Blind Weaponmaster: The "zen" conduct - beat the game while permanently blind.
 * Dungeon Bypass: The main idea of "digging for victory", and often invoked by real-time and minimum-turncount speedrunners - run down to reach the Castle as fast as possible, snag the wand and wish up a kit, and then win the game from there.
 * Flat Earth Atheist: The "atheist" conduct involves not using any of the religious elements of the game ({{spoiler|except for sacrificing the Amulet of Yendor, and even then, there's a patch that eliminates this, too}}), satisfying the technical specs of this trope.
 * Full-Frontal Assault: The "nudist" conduct - in other words, no armor whatsoever, meaning you'll have to find other ways to gain vital resistances and improve your defense.
 * Kill'Em All: The game also tracks whether or not you genocide other monsters and how many; related to this, the "extinctionist" conduct requires the player to render as many monsters in the game extinct as possible by killing enough of them.
 * Pacifist Run: It is possible for a very skilled player to win the game without personally killing anything; this often requires the use of powerful pets.
 * Speed Run: Naturally. The wiki has a list of speed ascensions, and speed play accounts for both in-game time (i.e. turn-count) and real-time.
 * Low-Level Run: The "protection racket" is a 'lesser' form of self-imposed challenge that seeks out as much gold as possible and beelines straight to Minetown to donate it all to a temple priest. Since donation effects are based on donating a certain amount of gold times your current experience level, protection racketeers will want to be as low-level as possible, and this is often part-and-parcel with Pacifist Runs (though these will need a way to level up for the quest eventually).
 * Set a Mook to Kill a Mook: Wearing the ring of conflict causes every nearby monster that isn't you to start attacking any other nearby monster including you!) The Sceptre of Might can also be invoked literally to generate conflict.
 * Shapeshifter Mode Lock: Amulets of unchanging can be worn for this effect, and rings of protection from shape changers can enforce this on other monsters, forcing them into their base form. This will also be enforced if you genocide your race/role while polymorphed - change back through any means and you will die.
 * Shock and Awe: Certain electric monsters have shocking attacks that can destroy your wands and rings in open inventory. There is also the wand of lightning (which is immune to blowing up from shock damage), the lightning spell sometimes used by hostile priests, and the lightning bolts from angry gods.
 * Shoplift and Die: Shopkeepers don't take kindly to being attacked or having their wares stolen, and will pursue you until you kill them, pay them back or otherwise pacify them.
 * Shout-Out: The game shouts out Rogue in the form of the Rogue level, and includes a lot of Dungeons & Dragons and The Lord of the Rings references - and many, 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! In addition, when Terry Pratchett passed away from Alzheimer's in early 2015, NetHack 3.6.0 (released later that year) contained a few tributes to the author:
 * Novels named after works in the Discworld series could be found in bookstores. Reading a novel displays a quotation from Pratchett's writings, and the first novel read gives 20 experience points.
 * Breaking expensive cameras may release an imp or a homunculus, as an homage to The Colour of Magic, where iconoscopes, the Discworld equivalent of cameras, each contain a 'picture-painting demon'.
 * Squeaky board traps now squeak in a specific pitch (e.g. "You hear a distant B flat squeak"); in The Light Fantastic, a character has floorboards tuned so he can determine not only if someone is approaching, but also where that person is standing.
 * {{spoiler|Death now speaks {{smallcaps|in all caps and without quotation marks}}}} in the same manner as the recurring Discworld character.
 * Dune - The worm tooth and crysknife are available as weapons.
 * Zork - zorkmids function as the game world's currency.
 * Sidequest: The Gnomish Mines, Fort Ludios, and Sokoban branches are all optional; Fort Ludios also isn't guaranteed to appear in a given game.
 * Silliness Switch: The hallucinations caused by potions, halluncination-inducing food (which essentially consists of corpses from monsters with stun attacks), and black lights serve as this. Non-hallucinating silliness includes kitchen sinks, tourists, cameras, Hawaiian shirts, and even the Keystone Kops.
 * Skeleton Key: Present and able to unlock any door or chest. The Rogue quest artifact is a magical thief-aiding key.
 * The NetHack 3.0 series introduced the unlocking tools, and had different kinds of keys that could only open corresponding types of locks; these were not regarded well generally, so 3.1.0 removed the shaped keys and allowed unlocking tools to open any door.
 * Songs in the Key of Lock: One way of opening the drawbridge to get into the Castle. A side effect allows you to easily kill off most of the monsters in the castle: {{spoiler|Playing the pass-tune again closes the drawbridge, and any monster on the drawbridge and porticullis squares will be crushed to death when it closes. Wash, rinse, repeat. This also destroys any loot they're carrying, though.}}
 * Sorting Algorithm of Weapon Effectiveness: Somewhat subverted, both for good and ill as far as the player is concerned.
 * Spell My Name with a "The": Used for some of the artifacts (e.g., The Eye of the Aethiopica, The Heart of Ahriman and The Magic Mirror of Merlin) and quest nemesis monsters (e.g., The Cyclops, The Dark One).
 * Spider Sense: The warning ability, available via intrinsic and extrinsic, highlights the location of nearby monsters with a number based on how dangerous said monster is. The searching intrinsic can also function as this to a degree, as it can automatically pick up on trap locations and hidden monsters before the player does.
 * Spikes of Doom: You fall into a pit! You land on a set of sharp iron spikes! {{spoiler|The spikes were poisoned! The poison was deadly...}}
 * 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". This can also occur for some other stats as well.
 * Storming the Castle: The Castle must be cleared to access the later half of the game, and has many a treasure that'll make it worth your while - and many a nasty monster standing between you and the loot.
 * Stuck Items: Cursed armour can't be removed, and cursed weapons can't be unwielded. There are several ways of dealing with these problems, though only one ("remove curse") will seem obvious.
 * Stupidity-Inducing Attack: Mind-flayers have an attack that reduces intelligence.
 * Suffer the Slings: Slings are an available weapon - although not particularly effective, ammunition is easy to come by. Cavemen start the game with a sling and a set of rocks and flint stones to throw, and hobbits are often found carrying them.
 * 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, monsters that aren't swimmers or amphibous also have Super Drowning Skills unless they have another means of crossing such as flight, levitation or breathlessness.
 * Super Not-Drowning Skills: On the other hand, aquatic, amphibious and swimming monsters - which include snakes and all "water"-based monsters - can cross over water tiles easily, as can you if you are in the appropriate form.
 * Super-Persistent Predator: "Covetous" monsters - including quest nemeses, Vlad the Impaler and the Wizard of Yendor - can warp to your location constantly, even on no-teleport levels. {{spoiler|Rodney himself will harass you even after you kill him - he can resurrect himself and/or teleport immediately to your location.}}
 * On a downplayed note, humans and various other monsters (hostile and otherwise) can follow the player to another level if they're on an adjacent square to the stairway or portal when you use them.
 * Super Strength: Conferred via gauntlets of power. Giants also have this, naturally, and so do nymphs (the better for them to pick up and steal items with).
 * Super Weapon, Average Joe: Humanoid monsters can find and use wands and artifact weapons just as capably as the player, which can lead to very weak monsters killing you with ease. The community term for some specific cases is "gnome with a wand of death".
 * Super Weight: You start at zero or occasionally one on All The Tropes's scale... except for the Tourist, who starts at negative one. You spend the game climbing the scale. {{spoiler|All the way to four.}}
 * Swamps Are Evil: Rooms on later floors in the main dungeon may contain swamps full of eels and fungi. {{spoiler|In Gehennom, Juiblex's lair is a gigantic swamp.}}
 * Taken for Granite: Can occur with Medusa as well as cockatrices, one of the game's many Goddamned Bats. {{spoiler|If you manage to kill the 'trice or its younger variant and it leaves a corpse, you can then wield its corpse, turning its power against your enemies. Make sure to wear gloves, though, and don't trip.}}
 * Talking Is a Free Action: Varies very much with the action in question. Since this is one of the earliest rogue-likes, the genre staple of "nothing moves until you move" is in effect. As for what is and isn't a free action...
 * Talking itself? Ohohoho, no it ain't. Using the extended #chat command to interact with a monster will print an appropriate response and use up a turn unless the monster in question has no response to give (as opposed to simply being unable to respond, e.g. due to sleep or paralysis).
 * Looking through your inventory is very much a free action, and is recommended before taking action in heated situations. You can also #adjust which letter each item (or stack of items) in the main inventory is tied to, as well as merge or spilt those stacks up, all without using any actual turns or actions.
 * You can use the quiver command to ready any projectiles you have for throwing via the fire command without using up actions.
 * The stethoscope can be freely applied once per turn - applying it again directly after that uses up the turn.
 * Technical Pacifist: See Pacifist Run above, and note that the requirement is that you don't personally kill anything. Softening up monsters for your pet dog or, say, leading an army of high-level pets through the dungeon and letting them slaughter everything you meet is just fine.
 * Tech Points: You need "skill slots" to advance a given skill, which are gained through amassing enough Experience Points and a certain number of successful uses for the item/spell in question.
 * Teleporters and Transporters: Teleport and level teleport traps randomly send you to another tile or level; vaults may have dedicated teleporters that send the user directly into them. Teleportation is also available via scroll and wand; both teleportation and teleport control also have ring and intrinsic forms, with the latter allowing you to select specifically where you end up. Certain characters can obtain teleport control via leveling up, and all playable characters can teleport at-will if they have teleportitis and are at least XL 12 (unless they're a wizard, who gets it earlier at XL 8).
 * Mass Teleportation: Breaking a teleport wand with charges left will cause a magical blast that teleports monsters caught inside it.
 * Random Teleportation: Intrinsic teleportation and extrinsic teleportation from a ring is known as "teleportitis", which will teleport you at random while moving. Leprechauns and nymphs teleport after successful theft attacks, and also teleport at random while moving - fittingly, their corpses are a potential course of teleportitis. Tengu also get around by teleporting and often warp specifically near you even when peaceful; eating their corpses can convey either teleportitis or teleport control.
 * Teleport Interdiction: A "no-teleport" condition occurs in the Sokoban branch, the home and goal levels of the quest, the Castle, the Valley of the Dead, and several other levels. Warping from covetous monsters ignores this, however.
 * Teleport Spam: Covetous monsters such as quest nemeses and some end bosses will constantly warp around you to attack, as well as teleporting to the up stairs to heal themselves when needed.
 * Ten-Second Flashlight: Averted. Most light sources can last quite a while, and the spell/scroll/wand of light creates a permanently lit area when used.
 * Throw the Book At Them: An unusual move, but it's possible here - and if it'll save your behind, you shouldn't discount it. Spellbooks can also be wielded.
 * To Hell and Back: The bottom half of the game takes place in Gehennom. Earlier NetHack versions literally had Hell instead, complete with {{spoiler|instantly frying you if you lacked fire resistance or lost it at any point within those levels}}.
 * Tomato in the Mirror: Can happen by chatting to specific bosses on the very last level of the game. "Who do you think you are, {{spoiler|War}}?"
 * 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 is the scroll of scare monster. Compared to the more easily-engraved and reusable Elbereth, it can scare monsters that even the engraving wouldn't ward off {{spoiler|(unless they're angelic beings)}} and works while you're blinded. You don't even have to read it - just stand on it and it'll work its magic! The catch is that you get to drop it once or maybe twice before it crumbles to dust when you next pick it up {{spoiler|(unless you can keep it blessed)}}.
 * Touch of Death: Many high-level enemy spellcasters can do this, including one of the end bosses, and getting the proper preventative gear is a common early-game priority. You can also use it if you learn the spell (which is more of a Death Ray), though actually learning and casting the spell are very difficult to do.
 * Trademark Favorite Food: Elves get the most out of the already-filling-for-its-weight lembas wafer; orcs tend to prefer raw meat and even tripe, and despise lembas.
 * Trial and Error Gameplay: The player is supposed to make out most gameplay mechanics this way. In a game with an immense 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. That said, the game does provide an Oracle, a special monster which gives valuable advice about the game, but she has great limitations on her consultations. There's also the in-game guides.
 * Turn Undead: Available through a spell, a wand, and a class attribute. Due to liberal application of Just for Pun, you can also use the former two to {{spoiler|revive corpses (turning them "un-dead"). Very useful when a high-leveled pet is killed, although beware - it won't always revive tame.}}
 * Underground Level: Most of the dungeon branches are this, with the exception of certain locations in some of the Quest branches.
 * Unicorns: One for each of the three alignments, and they're even eligible for riding as steeds. All three will try to keep a knight's move away from you, and you'll need to be pretty fast or sneaky to get next to one. Also, killing or sacrificing one of your own alignment is a really Bad Idea.
 * Unique Enemy:
 * The mail demon. It's a literal demon mailman that delivers messages from other users when playing on a server; on local machines, it can also deliver actual emails. The daemon normally appears and disappears within one turn without giving the player a chance to interact with it. However... {{spoiler|a Crazy Prepared player can kill it, rendering it extinct and preventing further messages from being delivered. To do this, the player needs to stone-to-flesh a statue of a mail daemon, which is not something that occurs naturally but needs to be wished for, and have enough speed and powerful enough weapons to kill the daemon in one turn - move too slow and it disappears with a cry of "I'm late!"}}
 * Only three Erinyes and nine Nazguls can be found in the dungeons. A popular Self-Imposed Challenge is to try ascending with {{spoiler|all of the Nazguls' invisibility rings, which they are guaranteed to appear with - this often includes naming them for [[The Lord of the Rings|each of the Rings from their source material}}.
 * Unexpected Gameplay Change:
 * The Rogue Level is a level that resembles Rogue: all-white ASCII in a different font, only monsters with a capital-letter glyph spawn, gold and other items use different glyphs, monsters don't leave corpses upon death, and doorways cannot be entered diagonally.
 * The Sokoban branch prevents teleporting within its levels and won't let you move boulders diagonally until you complete the floor; unlike the namesake game, boulders can be created, broken, teleported, transformed, or even squeezed past, though there's a Luck penalty for most of these.
 * Unusable Enemy Equipment: Averted. If an enemy has it, you can kill them and use it - provided it doesn't kill you first. Some monsters have a starting inventory and most monsters also have death drops, so it can be hard to tell which one an object qualifies as if the monster dies without a chance to use the item. Getting particular items such as wands of death, potions of gain level, and {{spoiler|the amulet of life saving}} off enemies is particularly frustrating.
 * "That was my prized wand of nothing, You Bastard! I was saving that!"
 * Unwinnable: If you {{spoiler|convert by sacrificing at another god's altar before spoiler|your quest master gives you the okay to go on your quest}}, you'll be unable to {{spoiler|get the Bell of Opening}} and complete the game. {{spoiler|Attacking your quest master before getting permission to go on the quest also accomplishes this, as does failing the alignment test seven times.}}
 * Unwinnable by Insanity: In fairness, the listed scenarios are things you essentially have to go out of your way to do in most instances, or else have a very unfortunate series of accidents.
 * Useless Useful Stealth: Averted - stealth can be a very good intrinsic to have, especially when clearing out monster-filled zoos such as the one in Sokoban. Even in a scenario where kicking or causing something to explode wakes the entire room of monsters up, you still have plenty of other crowd control skills you can fall back on. Stealth also has multiple sources (including some elven gear and even a godly gift), and some roles gain it through leveling up.
 * Vancian Magic: The spellcasting system used in older versions of NetHack; the Wizard Patch for SLASH'EM exchanged this for a more standard Magic Points system, and was fully merged into the main line of releases as of version 3.3.0. Wands still operate on this logic to a degree, requiring no magical aptitude to use but possessing a limited number of charges. Scrolls are similar as well, allowing one casting of a given spell per scroll read, and many wands and scrolls have a spell counterpart (e.g., cancellation, fireball, identify, remove curse).
 * Veganism and Vegetarianism: NetHack tracks conducts for both vegan and vegetarian diets. The Monk role in particular is expected to maintain at least a vegetarian diet, with small alignment penalties occurring each time they consume meat.
 * Video Game Caring Potential:
 * Helping a monster out of a trap may make it peaceful, and you also might get an alignment boost if you're lawful.
 * Players consider it very poor form to mistreat Izchak (named for deceased DevTeam member Izchak Miller), even those who generally dislike or otherwise try to kill shopkeepers - often, he is even spared by extinctionists!
 * Video Game Cruelty Potential: There's a lot of asshole things you can do without being immediately punished for it, though not without penalty completely.
 * 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, and will come down on you hard for acting inappropriately. This doesn't necessarily mean you're supposed to be well-behaved - at minimum, you're not supposed to be caught. Or, in some people's minds, it means surviving the very wrath of God. Which is doable. {{spoiler|You can survive the lightning bolt with an amulet of reflection, and the wide-angle disintegration beam by eating a black dragon's corpse. And best of all is your god's response: "I believe it not!"}}
 * Villain Teleportation: "Covetous" monsters can warp to you freely, even on no-teleport levels, and will teleport to the upstairs to heal - and, with a couple of exceptions, they are always hostile towards you. {{spoiler|Inverted with covetous pets: A tamed lich that grows up to become a master lich or arch-lich will teleport to stay near you when moving normally, which in practice makes keeping track of it fairly easy - but start worrying if it gets confused...}}
 * Violation of Common Sense: Tends to occur with some of the more creative solutions to in-game problems that players devise. {{spoiler|For example, slowly turning into a green slime? Just cure it by manuallly polymorphing into a green slime!}}
 * Voluntary Shapeshifting: Possible through polymorph control and a means of inducing the polymorph at will, e.g. a wand, potion, or polymorph trap.
 * Wafer-Thin Mint: If you're oversatiated, 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. {{spoiler|Amulets of magical breathing can prevent this, and there's a few other methods as well.}}
 * Walking on Water: Possible via water walking boots. Monsters capable of crossing water by 'swimming' (among other methods) will also appear to "walk" on the water.
 * Walk, Don't Swim: The player can do this by walking into a pool with magical breathing. Regardless of whether or not you have it, you'll sink to the bottom, causing your entire inventory to end up wet (except for items in an oilskin bag) - if you do, however, you can survive and walk around underwater, pick up items such as kelp fronds lying at the bottom, though you'll also be pushed around by the currents.
 * Was Once a Man: Certain bones files may generate monsters such as mummies and wraiths instead of ghosts, which is only possible through specific deaths (e.g. {{spoiler|being killed by a wraith or a Nazgul}}).
 * We Buy Anything: Subverted; most shops outside of general stores (which play this straight for the most part) specialize and will only buy whatever types of items they sell. 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.
 * Also played straight in that any shop will sell the player anything that comes into the shopkeeper's possession (including the items of monsters killed in the store).
 * Weak but Skilled: Several classes, such as the Caveman and Tourist. Also a good mindset for the player themselves, especially in the early game.
 * Weakened by the Light: Gremlins fear light to the point that using a light-producing item or spell near them actually causes damage and forces them to flee.
 * Weaksauce Weakness: Several late-game monsters have surprising weaknesses, including quest nemeses and even the last few bosses. {{spoiler|Pestilence and Famine can be dropped (at least temporarily) with a wand of death, and tooled horns can even scare them and Death off for a while.}}
 * Weapon of Choice:
 * Monsters belonging to a species with their own variant of a given weapon or set of armor will generate with those where possible - orcish monsters will frequently generate with orcish armor and daggers, elven monsters will often generate with elven armor and weapons, and dwarves will generate most often with dwarvish armor and weapons. Playing as one of these species also gives you intrinsic knowledge of their respective items.
 * Various monsters also have a specific weapon or weapon type that they are guaranteed or at least favored to be generated with (e.g., orcish monsters and scimitars, or ogres and clubs). Gnomes are unusual with respect to the aklys, as it isn't actually a gnomish weapon - it can be generated on any monster that doesn't have the "strong" attribute and can use a weapon, but has not received one; gnomes fall into that subgroup and are spawned in large numbers, particularly in the Gnomish Mines, and may be the first such monster you encounter.
 * Weapon of X-Slaying: Commonly referred to as the "Banes" - there's Orcrist and Sting (orcs); Ogresmasher, Giantslayer, Werebane, Demonbane, Dragonbane, and Trollsbane (Exactly What It Says on the Tin); and Sunsword (undead). The Sceptre of Might has a double-damage bonus against monsters with a different alignment from you.
 * Parodied by Vladsbane, a reference to how Vlad the Impaler was so easily defeated in previous versions that players made it a point to use the most impractical weapons possible for some semblance of a challenge.
 * Also "parodied" by Puddingbane, used for any similarly weak-on-purpose weapon employed while pudding farming - the act of splitting puddings to make as many as possible before killing them for the rewards - in older versions.
 * 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:
 * What Measure Is a Humanoid?/What Measure Is a Non-Human?:
 * For non-chaotics, murder penalties only apply if you kill "always peaceful" humans (e.g. watchmen, shopkeepers, etc.); many other peaceful non-human monsters incur a minor alignment penalty in comparison unless they were coaligned or you killed them without angering them.
 * On that note, player characters are generally forbidden from sacrificing members of their own species (unless Chaotic) or eating corpses of their species (unless the player is an orc or Caveman). Every other being they come across - including many sentient and even sapient monsters? Fair game!
 * Whip It Good: Bullwhips are an available weapon type. Adventurer Archaeologists start with a +2 bullwhip, and balrogs and some horned devils will generate with one. Bullwhips are subpar as weapons, but also provide a valuable utility in disarming other monsters, which naturally can also be done to you.
 * With This Herring: The Tourist class is the most obvious example, but several other classes qualify.
 * A Worldwide Punomenon: NetHack as a game runs entirely on this. Levitating characters will sink to the ground 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; and 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". And that's just for starters! Boy howdy, The Dev Team Thinks of Everything.
 * 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). {{spoiler|This applies even after you've killed him, with a slightly different taunt applied.}}
 * Several high-level covetous monsters, including the Wizard, will also teleport to your location constantly as long as you are on the same level. All of them combine this with "Get Back Here!" Boss (mentioned above) for maximum annoyance.
 * {{spoiler|The Riders implement this in an unusual way - trying to teleport them or their corpses away has a 12/13 chance of warping them right next to you.}}

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