* AnticlimaxBoss: Lord Surtur, the Goblin King (in the days when Elf was a character class), the Master Assassin, and Vlad the Impaler.
** Vlad is so anti-climatic that it's become a RunningGag to [[CherryTapping Cherry Tap]] him to death with -3 throughly corroded orcish daggers, thrown scrolls, and other such things, and name the object in question "Vladbane"
* BreatherBoss: Croesus.
* BrokenBase: Two of the major arguments in fandom have been:
** Should the game be played using the graphical tile-sets or the original ASCII format?
** Is it a legitimate tactic to exploit programming quirks which allow such things as "pudding farming" (see below)?
* DemonicSpiders: There's ''at least'' two or three at any point:
** On early levels, you have to deal with Floating Eyes which [[StandardStatusEffects paralyze]] you, Gas Spores which [[ActionBomb do obscene damage by exploding when they die]], and killer bees.
*** Floating Eyes can be avoided, killer bees can be Elberethed, but may The Lady help you when your pet decides to start attacking that gas spore that's adjacent to you.....
** On early-middling levels, you have to deal with Soldier Ants -- the most common enemy-based cause of death in the game (accounting for 1.75% of all deaths on nethack.alt.org. [[http://nethackwiki.com/wiki/Ant#.22Go_Team_Ant.22 Go team ant!]])
** On the middling levels, you have the infamous Cockatrices and many enemies who will swallow you and kill you, including Lurkers and Purple Worms (which can also be encountered on the earlier levels).
** Then you must contend with Demon Lords and Princes, and should you actually ''survive'' them and get the Amulet of Yendor, you must face an infinite amount of more and more powerful Wizards of Yendor, and the consistently respawning Riders of the Apocalypse: Death, Pestilence, and Famine. [[spoiler:You're War.]]
* FridgeHorror: There are lots of "used armor" shops scattered throughout the dungeons. Sometimes these shops contain cursed armor, which can't be removed, except by uncursing it or if the original owner dies wearing it. The horror comes when you realize where the shopkeeper gets his inventory.
** And if you die in a shop, the game flat-out tells you that the shopkeeper takes all your possessions.
** If you somehow directly steal from the shop (Teleporting with unpaid items, digging out,....), the shop owner will chase you. When you die, guess who comes for the loot?
* GameBreaker: A very controversial thing to do in Nethack is "Pudding Farming", causing an enemy that splits into two whenever you attack it to split multiple times to abuse the game's prayer and sacrifice systems. A similar thing is to repeatedly kill a boss that is on the last level of the game. This boss reincarnates an infinite number of times, but gives a full score each time, meaning with the proper setup, hitting the max score is [[http://groups.google.com/group/rec.games.roguelike.nethack/msg/beddbbf83d4a369d trivial]] (but that's OK, since in Nethack, it's generally considered a sign of skill to ascend with a lower score rather than a higher one).
** The [[TheDevTeamThinksOfEverything DevTeam]] implemented an immediate and savage punishment for pudding farmers. It's called Pudding Farming.
*** Also, nearly anything you'd accomplish with Pudding Farming won't help you on the astral plane.
* GeniusBonus: Many things in Nethack, including some of its {{Shout Out}}s, are very subtle. For example, there is an enemy named the "quantum mechanic" which sometimes carries a box. Inside the box is a cat named Schrodinger's cat, which has a 50/50 chance of being either alive or dead. If you examine the game's source code, you will learn that the state of the cat is not determined until you open the box. Some fantasy items benefit you if you know the myths without even having read a spoiler: [[spoiler:{{Unicorn}} horns heal, clay {{Golem}}s can be [[TheDevTeamThinksOfEverything destroyed]] by erasing their writing, amethysts (which literally means "not drunk") convert booze to water.]]
** Since the game has strong Unix origins, there's also plenty of jokes only a Unix/Linux geek would understand.
* GoddamnedBats: Nymphs, Floating Eyes, and Leprechauns, to name a few.
* HilariousInHindsight: The line at the end of the introduction to the game is "Have Fun, and Happy Hacking!". Fun. [[DwarfFortress With a capital F]].
* NightmareFuel: For a game that uses ASCII graphics, this game has its fair share.
** Abandoned temples. Upon entry, there's a random chance you'll be paralyzed by a massive ghost.
** Beehives can make those who are fatally allergic to bee stings extremely uneasy.
** Green slimes that cause your body to decay and transform into a green slime. The process is described in BrainBleach-inducing detail as you slowly turn into slime.
* ScrappyLevel: Gehennom. Actually, 20 to 24 ''consecutive'' {{Scrappy Level}}s.
** One of the many additions VideoGame/SlashEM makes is breaking up the monotony of Gehennom with more "special" levels.
** Sporkhack completely revamps Gehennom by (a) giving the local {{mooks}} some ability to actually threaten the player (b) getting rid of the mazes in favour of caves (with lava behind the cave walls).
* Scrub[=/=]StopHavingFunGuys: Don't get caught using any movement key configuration other than HJKLYUBN. Or ''maybe'' numpad. Don't admit to using the tile graphics, either.
** Beyond this, players' [[InternetBackdraft personal rulebooks]] get complicated. Abusing [[GoodBadBugs borderline glitches]] is seen as legal by some (and denigrated by others), and while [[{{Walkthrough}} avoiding trial-and-error by liberal use of the spoileriffic wiki]] used to be seen as bad form, it's now more or less accepted in the age of the Internet.
* ThatOneBoss: Master Kaen (the Monk quest nemesis) and Demogorgon both qualify, as (due to his propensity for coming back with more hit points and a higher caster level than before) does the Wizard of Yendor.