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"As you walk through the main entrance of the base, you hear animal-like growls echoing throughout the distant corridors. They know you're here. There's no turning back now."
The game's manual

Doom, id Software's December 1993 follow-up to Wolfenstein 3-D, was an astronomical leap forward in video game design, and an even bigger step when it comes to video game violence.

Our hero is an unnamed space marine (nicknamed Doomguy) who, after putting his commanding officer in a full-body cast for ordering him to fire at innocent civilians, was assigned to the Union Aerospace Corporation base on Phobos, one of the moons of Mars. Teleportation experiments between Phobos and Deimos cause the latter to vanish and open up a portal to allow hordes of hellbound monsters to invade the Phobos base, leaving the marine as the only survivor. While searching for a way off Phobos, he instead finds himself transported to Deimos, now residing in the creatures' homeland, which turns out to be none other than Hell itself.


The release of Doom was met with unprecedented and massive controversy regarding its content. Not only was there a very high amount of explicit Satanic imagery (albeit all cast in a highly negative light), it was filled with graphic depictions of zombies and monsters being blown up, eviscerated, shot to pieces and generally disintegrating into piles of gore. People who play video games, however, would have referred to all of the above as "lots of fun for the whole family!"

Gameplay was extremely gung-ho and to-the-point — the developers noted that the manual could have simply read, "If it moves, kill it" — and encouraged the player to attack with reckless abandon, using such implements as a chainsaw, your own bloody fists, shotguns, machine guns and the almighty BFG, a massive weapon which could reduce entire rooms of monsters to viscera. Even the player's own face, shown in-between the health and armor counter, became increasingly battered and bloodied with damage like in Wolfenstein.


Also, whereas Wolfenstein's fortresses all had identical lighting and walls that were always the same height, always aligned in perfect 90º angles, and always with a minimum distance between corners or another wall, Doom featured variable lighting (including flickering and glowing lights, adding to the game's atmosphere), differing vertical heights, and walls that could be angled at any orientation and have any amount of distance to a corner or between walls (including distances too small for you or an enemy to walk through).

Another feature was expansion of the weapons. Wolfenstein's weapons all behaved identically as hitscan weapons, with only the rate of fire changing. Doom's weapons would include both hitscan, and projectile weapons which enemies could dodge, as well as splash damage weapons and the legendary BFG. This made the arsenal more flexible, with weapons more suited to certain situations. Enemy attacks were similarly diversified, making combat far more dynamic than it had been in Wolfenstein.

The game also introduced the idea of multiplayer death matches and co-op missions in a modern FPS, with its developers fully expecting Doom to be the biggest cause of decreased productivity in IT companies the world over in 1993. And they were right. It became such a smash hit that it is often credited with boosting the sales of Microsoft Windows 95, with even Bill Gates crediting it for popularizing the OS, thanks in part to his efforts to make sure there was a Win95-compatible version of the game after realizing that Doom was installed on more computers than Windows 95.

Doom built upon the formula established by Wolfenstein 3D and expanded upon it, becoming a Trope Codifier to the entire first-person shooter genre — to the point where through most of the 90s, until true 3D games really took off and started emerging from Doom's shadow, such games were often referred to as "Doom clones" as opposed to "first-person shooters". Doom's weapon selection would form the template from which many other games would base their own weapons on. The deathmatch would become a staple of multiplayer FPS to this day. Even the game's basic premise would become a trope.

Doom was also incredibly moddable, giving birth to one of the first big video game modding communities (which first operated on BBS before migrating to the internet), which still thrives and exists to this day. Doom also played a crucial role in popularizing the idea of the speedrun, as each end level score card not only keeps track of how long the player took to complete the game (alongside various completion percentages), but also included a Par time set by the games' creators, encouraging players to beat it, and keep finishing each level faster and faster. The ability to save runs as demo files also made sharing runs easy in an era where sharing videos over the internet was nigh impossible. It's no exaggeration to say that Doom is one of the most influential games of all time.

Doom has been ported to many, many console systems over the years. The PlayStation and Sega Saturn versions combined levels from both Doom and Doom II alongside a large number of unique missions; more original levels were released in a sequel entitled Final Doom. Doom's source code has been released, and, at this point, almost anything with a CPU in it — many cameras and music players, some watches, several appliances, even a graphing calculator has been shown to run it for about half a minute before crashing — has had a version of Doom released for it. The common "it runs Doom" joke about fans modding the game to run on refrigerator displays, Etch-a-Sketches, Babbage's difference engine aren't far off the mark at this point. The game also used a creepy and distinctive sound effect for doors opening, which has been re-used in many Speculative Fiction series for all sorts of things.

Sequels and other media

Doom II: Hell on Earth (1994) sees the demons invading Earth. It was also a huge financial and critical success. Final Doom was released the same month as Quake; it was identical to Doom II, but came with two different Expansion Packs: TNT: Evilution, created by the third party modding group TeamTNT (originally intended to be free until id struck a publishing deal with them at the last minute); and The Plutonia Experiment, made by two members of the group in four months' time, generally considered the hardest of the official packs. Final Doom was also the game that included a 32-bit DirectX version of the Doom engine, making it possible play Doom on Windows 95/98 and XP machines, besides virtual machines like DOSBox or the many source ports. It received another updated port utilizing the Unity engine for PlayStation 4, Xbox One, Nintendo Switch, iOS, and Android systems in 2019, followed by a PC version in 2020 that allows players to enjoy Doom on their favorite console, handhelds, or natively on modern Windows systems with various enhancements and a selection of curated community-made mods through Its PC and iOS/Android versions also has the ability of side-loading custom vanilla-compatible and DeHackEd supported WADs.

The third game in the series is Doom 64 for the Nintendo 64 in 1997. Running on a modified version of the Doom engine, it has the Marine returning to Mars to investigate a resurgence in demon activity. As the title suggests, it was an N64 exclusive for 23 years until a remastered port by Nightdive Studios (complete with a new epilogue campaign) was finally released for PC, PlayStation 4, Xbox One, and Switch on March 20, 2020.

A decade later, Doom 3 (2004) was released. Actually the fourth installment, and also a reboot rather than a sequel, it breaks with the first three significantly, with a dark, oppressive tone much more akin to a Survival Horror than anything. It was this incarnation on which the first movie was based. This was followed by the expansion pack Resurrection of Evil, set two years later. The game was remastered in HD, compiling the first two games with it, in addition to adding another eight levels to its campaign. Furthermore, you can actually wield a flashlight and a gun at the same time. This compilation, titled the BFG Edition, was released in October 2012.

In 2016, id Software released another game simply titled Doom, a re-railing of the Doom franchise, known to most fans as Doom 4 or Doom 2016. Doom used to be known as Doom 4 when it was revealed in 2007, but the game went through Troubled Production, so id decided to revive it. The reboot is more of an Actionized Sequel compared to Doom 3, featuring faster gameplay and more emphasis on shooting rather than horror. It also purposely calls back to the gameplay of the first two titles by avoiding modern FPS mechanics like emphasis on cover, weapon reloading, and limited weapon loadouts. A sequel, DOOM Eternal, was released in March 2020.

Also, a comic for Doom was made at the height of the dark age. It's hilarious, probably intentionally so. We hope. As mentioned above, there was also a movie for it, which is of debatable quality, but maintains some of the satanic imagery and violence.

There was also a series of novelizations by Dafydd ab Hugh and Brad Linaweaver. Four in all, the first two, Knee Deep in the Dead and Hell on Earth, were based on the first and second games, respectively. The final two, Infernal Sky and Endgame, went their own direction with the plot. These novels have a small cult following. There are also two novels based on Doom 3 by Matthew Costello, who also wrote that game's script.

As for other products in the franchise, there are two cell phone-based RPGs, an iOS-based Rail Shooter, and a board game with expansion pack. For mods and fan games, see FanWorks.Doom.

This video game is the Trope Namer for:

This video game provides examples of:

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  • 100% Completion: Each level ends with percentage counters for how many monsters were killed, items collected, and secrets found. Some source ports will reward you with a "Perfect" rating if you get 100% in all three categories. Most 100% speedrun categories (eg: UV-Max) focus only on 100% monsters and secrets.
  • 12-Bar Blues: A large number of songs use this chord progression in some form, most famously At Doom's Gate (E1M1). On The Hunt (E1M6) also uses it, while The Imp's Song (E1M2) uses a slower, corrupted version of it.
  • All There in the Manual:
    • The manual gives the backstory for the game in fairly elaborate detail. The ending text of Episode 1 even seems to assume that you've read it, making reference to "the missing Deimos base" without further explanation, which would only make sense if you read the synopsis.
    • Also, the novelizations are the only time "Doomguy" is given a proper name (for those wondering, it's Flynn "Fly" Taggart for the classic series novels, and John Kane for the Doom 3 novels). Word of God is that the games' protagonist is deliberately not given a name because it's supposed to be you, the player.
  • Always Chaotic Evil: The demons all have nothing but malicious intent towards everyone and everything around them - even other demons, if one of them hits another.
  • Ammunition Backpack: As a power-up. Not only does it give you one of each "small ammo pack" (one pistol magazine, four shotgun shells, one rocket, and one 20-volt energy cell), if it's your first, it doubles your ammo-carrying capacity (you can carry 400 bullets and 100 shells instead of 200 and 50, and so on).
  • And I Must Scream: Some crushing floors in the first two games only crush, they never release. If you let yourself be smashed by these and happen to have enough health, you'll remain trapped alive in concrete. Have a nice stay if it's multiplayer and no one else can find and kill you to release you. Thankfully, a rather rare bug.
  • And Your Little Dog, Too!: In the ending of the first game, the demons are busy invading Earth, but they take the time to kill Doomguy's pet rabbit, Daisy, and mount her head on a pike just to be dicks.
  • Anti-Frustration Features:
    • In the original games, the highest and lowest difficulties both doubled ammo. In the case of the latter, it's an obvious "make it easier by letting the player spam stronger guns", but in the case of the former, you'll need the double ammo drops to handle the increased quantity of eternally respawning enemies.
    • The game normally switches weapons automatically if you're out of ammo for your current one (such as switching from the chaingun to shotgun if you are out of bullets but still have shells). However, the game will never switch you to the rocket launcher (even if the only other weapon available is the fist), as it would be way too easy to blow yourself up if this happened in the middle of a pitched battle.
  • Armor Meter: You have separate armour and hit point tracks. Armour absorbs a set percentage of hit point damage depending on its colour: 33% for green armour and 50% for blue. Counterintuitively, this means collecting green armour within a certain range of values can actually make you more vulnerable.
  • Arrange Mode:
    • In the Harder Than Hard "Nightmare!" difficulty, monster projectiles are faster, Pinky demons move faster, and enemies respawn several seconds after death. Oh, and you can't use console cheats. You also recieve the same doubled ammo bonus as in the "I'm Too Young To Die!" difficulty. You'll need it.
    • The 2019 Unity ports added an "Ultra-Violence+" difficulty in between Ultra-Violence and Nightmare!, which features faster enemies and weapons available from the multiplayer modes without the respawning monsters from Nightmare! mode.
  • The Artifact: The computer screens in the star textures contain the text "Tei Tenga" left over from Tom Hall's Doom Bible where the game was planned to be set on an alien world. After Tom was voted off the island, the game moved to Mars' moons.
  • Artificial Stupidity:
    • It doesn't matter if a fellow monster is in the way, all monsters will start attacking upon sight of the player, and if their attack connects with a fellow monster, they'll turn on each other. Players who are out of ammo will quickly learn to start triggering in-fights. The term "monster infighting" was coined to describe this (especially when other games began featuring the same thing).
    • Pinkies will always charge straight at the player, regardless of what's in their way. If you've got the chainsaw, all you have to do is hold down the fire button and they'll happily charge right into your blade and get torn apart.
  • Artistic License – Space: The original Doom takes place on Mars' moons, Phobos in episode 1 and Deimos in episode 2, which are depicted as having Earthlike gravity and atmospheres. In reality Phobos and Deimos are tiny moonlets no more than 20 kilometers across, have gravity so low you could probably jump into space off them, and have no atmosphere (and even if you could artificially generate one, the gravity of the moons would not be enough to keep it from floating away).
  • Ascended Glitch: Oh, wow. Lots. Most of them have been used and abused for speedruns and map-making.
    • The shimmery "hall of mirrors" effect that occurs when a texture is missing has been adopted by some level designers to create deep water. It will still glitch if your view is below the water level, however.
    • Also the "voodoo doll" bug, which can be easily created by placing two different start points for a single player. Clever mapmakers have used this bug to create traps which can teleport a player into another copy of himself, resulting in a recursive Tele-Frag (MAP30 of TNT: Evilution is an example). Voodoo dolls under triggered crushing ceilings can also be used to cause player deaths wherever the mapmaker wants; for example, simulating bottomless pits by triggering the ceiling if a player falls into one, or giving a time limit by having a descending ceiling which will eventually crush the voodoo doll.
    • It is possible to mess with sectors and sector references to create an "invisible staircase" effect, which was first demonstrated by a map called UAC_Dead.wad. This in fact abuses the same glitch as deep water effect above, just the water doesn't need some of the set-up needed for bridges.
    • If you trigger an action to move the floor up, but the target height is lower than current height, then the floor will move instantly (and the other way round, if the floor should be moving down but the target height is higher, it will also move instantly). Combined with the "invisible bridge" effect above, this allows for a fake 3D bridge which can be passed over and under, by moving the floor depending on where the player is. This is used in some custom maps. It is also used heavily in Doom 64 to create bridges and tunnels.
    • Under the right circumstances, it's possible to finish a level while (or even after) dying, causing you to start the next one with the standard 100 health units and pistol with 50 shots. The "suicide exit" technique is often employed by speedrunners, as Doomguy's corpse can fit through places he can't. Some user-generated maps are actually designed to invoke this on purpose (known as a "death exit" or "forced suicide exit"), in order to deprive the player of their arsenal ready for the next level.
  • As the Good Book Says...: The entirety of "Thy Flesh Consumed" and eight of its nine levels have titles that are referenced from the King James version of The Bible:
    • "Hell Beneath" is taken from Proverbs 15:24.
    • "Perfect Hatred" and "Against Thee Wickedly" are taken from the verses of Psalm 139, verses 20 and 22.
    • "Sever the Wicked" is taken from Matthew 13:49, which is an excerpt from the Parable of the Fishing Net (13:47-50).
    • "Unruly Evil" is taken from James 3:8.
    • "They Will Repent" is taken from Luke 16:30, which is also an excerpt from the Parable of the Rich Man and Lazarus (Luke 16:19-31).
    • "And Hell Followed" is taken from the Book of Revelation, Chapter 6, verse 8.note 
    • The episode title itself ("Thy Flesh Consumed") and that of its final mission ("Unto the Cruel") are taken from the two verses of Proverbs 5, verses 9 and 11, respectively.note 
  • A-Team Firing: Normally, monsters fire directly at the player, allowing the player to dodge. If you collect the Partial Invisibility power-up, enemies will fire wildly in your general direction (and miss more often than not). Ironically, this can actually make it harder to avoid getting hit sometimes if you pick up a bad habit of dodging projectiles or if there are a lot of enemies in an area, because you can accidentally dodge into one of the stray ones; most custom maps use the sphere for this purpose, by forcing you to collect one before entering a large battle with a lot of demons. However, the Powerup is surprisingly good when dealing with hitscan enemies, since you can't dodge their bullets and Partial Invisibility will mess up the RNG and make them miss almost all the time, saving you a lot of pain.
  • Attract Mode: The game will play a demo if left on the title screen for a second or two.
  • Auto-Save: Many source ports, such as ZDoom or Zandronum, auto-save whenever the player enters a new level, whilst also having the option of manual saves.
  • Awesome, but Impractical: The Berserk pack. It brings you back up to 100 health if you're anywhere below that, which is a godsend if you're down to 10 or 20 health. On top of that, as its name implies, it boosts the power of your punches for the rest of the level to the point you can gib zombies and imps with one or two hits. But why would you risk rushing into a horde of enemies to punch them to death one at a time while the others tear you to shreds? It's mostly good for ammo-crunch situations.
  • Back That Light Up:
    • The Game Boy Advance version of Doom had more than one color scheme to compensate for the different lighting possibilities for that system.
    • An early patch added several "gamma correction" settings to lighten the game, to help compensate for the terrible backlighting of CRT monitors commonplace at the time.
  • Badass Normal: The marine. Even the manual outright calls him the "toughest space trooper ever to suck vacuum."
  • Bare Your Midriff: A rare male example. The marine on the cover art has his belly exposed. This seems to be a very strange armour design choice, but looking closely at the actual art (The in-game digitization is a bit harder to make out) shows the chest hole was torn open.
  • BFG: Not just any BFG, either, but the BFG.
  • Big Labyrinthine Building: Almost an uber-example of this trope, with many levels taking place in gargantuan buildings.
  • Big Red Devil: The Barons of Hell evoke this the most, looking like satyrs with pinkish-red torsos. With different colorations, the Cyberdemon and Hell Knight are pretty close to this trope as well.
  • Black-and-White Morality: All the Doom games, really. Monsters from Hell trash humanity For the Evulz. You have lots of guns. Monsters goo-ify quite nicely. There's not a lot of ambiguity when it comes to what you're supposed to do.
  • Black Blood: Enemies bleed green in the Game Boy Advance ports of Doom and Doom II.
  • Blackout Basement: The games have a fair share of darker levels. Spectres tend to lurk around these in larger numbers than usual, and sometimes, you may just find a Light Amplification Visor. In the worst offenders, it's easier to navigate looking at the automap. Particular standouts in the first game are the penultimate room of E1M5, "Phobos Lab", and the southwestern portion of E2M6, "Halls of the Damned".
  • Blatant Item Placement: In Doom/Doom II, it's rare that item collection triggers an ambush or trap, but some do exist. However, some items are shown on display (e.g. the armor in E1M1) for no reason.
  • Blood from the Mouth: The marine's portrait whenever his health is low enough.
  • Bloody Bowels of Hell: A lot of the "hell" levels of the original Doom and Doom II. Walls of skin that's sometimes wounded or peeling off and floors made out of intestines are commonplace, at least one room has walls made out of large numbers of corpses compacted together, and boiling blood is a common type of hazardous floor.
  • Body Horror: The original Doom games have plenty of walls in the hell levels appearing to be made of human flesh, faces, or piles of corpses.
  • Boring, but Practical: Your trusty ol' shotgun. It does pack a decent punch, especially up close to an enemy. And ammo for it is relatively quite plentiful compared to the more exotic weaponry like the plasma gun or BFG. Also, due to its rather decent amount of damage output, the shotgun is also pretty good at dealing with most common enemies.
  • Boss in Mook Clothing: Barons of Hell are just plain tough with 1000 hitpoints, so killing one with anything weaker than the rocket launcher is a prolonged waste of ammo, and where there's one Baron, there are likely more.
  • Bottomless Magazines: Downplayed; you have a finite amount of ammunition for every weapon, but you never have to reload.
  • Bowdlerise:
    • Swastikas in E1M4 in Doom were changed in later versions to allow the game to be sold in Germany.
    • The Game Boy Advance ports of Doom I and II had all the in-game blood turned green — which had the side effect of turning objects such as shotgun shells, pipes on walls and other items green as well, since they merely changed the base palette. Enemies no longer explode into bloody chunks as well, resulting in these ports getting a Teen Rating by the ESRB. Ironically, the SNES port of Doom retained most of the original game's red-blooded violence, with only the Satanic symbols being censored.
    • In the 2019 Unity ports of Doom, its version of REKKR features valkyrie statues that were originally nude but was changed to be clad in armor instead. However, according to one of the mod's authors, he doesn't mind this change and prefers the armored version.
  • Brain Monster: The first final boss - the Spider Mastermind - was essentially a giant brain carried by a robot body.
  • Canon Welding: The cell phone RPGs are in the same continuity as Wolfenstein RPG, which features the "Harbinger of Doom" as the final boss. The Harbinger gets his arm and leg blown off and swears to avenge himself on B.J.'s descendants, becoming the Cyberdemon.
  • Chainsaw Good: Fondly remembered and one of the iconic weapons of the series.
  • Chuck Cunningham Syndrome/Shoo Out the Clowns: The Yorps, Gargs, and other aliens living on Mars in the Commander Keen series are inexplicably absent from Doom and all of its follow-ups, despite the fact that both series share a universe. But at least the original series excused this absence by having none of the games actually take place on Mars itself. Besides, having cute little alien critters running around would've probably clashed with the Darker and Edgier tone of Doom.
  • Classic Cheat Code: iddqd, idkfa, idchoppers, and so on.
  • Clothing Damage: As seen in the page image, Doomguy's uniform is heavily damaged in most official artwork. Amusingly, this led to some players thinking that his armor was issued with an abdominal cutout.
  • Compilation Rerelease: The classic series has been included few compilations across PC and other platforms.
    • The id Anthology not only compiles of all the classic Doom games, it also includes Wolfenstein 3-D, Quake, and the entire Commander Keen series across four CD-ROMs. This collection also added some bug fixes to TNT: Evilution and The Plutonia Experiment, and this version serves as the basis of the release.
    • The Depths of Doom Trilogy is a PC compilation that included The Ultimate Doom, Doom II, and Master Levels for Doom II across three CDs, along with the shareware version of Heretic, an amateur set of levels called Maximum Doom, and DWANGO version 2.02 for multiplayer at the time.
    • Doom: Collector's Edition for PC includes The Ultimate Doom, Doom II, and Final Doom on a single disc. It also allows players to play the classic Doom games without using virtual machines such as DOSBox or source ports.
    • The BFG Edition includes Doom and Doom II, albeit the Xbox LIVE Arcade ports that have various alterations including the censored versions of the Wolfenstein 3D secret levels in Doom II... on the plus side, it gives PC players a chance to officially play the Doom II XBLA-exclusive episode "No Rest For the Living". In November 2012, the PlayStation 3 received another compilation called Doom Classic Complete, which includes the original two games plus "No Rest for the Living", as well as Master Levels for Doom II and Final Doom, marking the first time in a long while that TNT Evilution and The Plutonia Experiment have been seen on home consoles.
  • The Computer Is a Cheating Bastard: A combination of Fake Difficulty and bastard map-designers, it does not matter how carefully a player clears rooms and watches dark corners as there will always be tiny, function-less, hidden, and effectively-invisible closets containing idle monsters whose sole purpose is to surprise the player from behind.
    • And, to a lesser extent, there's the way hitscan enemies (i.e. riflemen, shotgunners, spiderdemons, etc) can pseudo-randomly aimbot you at any range, even if they're a single pixel on a distant mountain. While this doesn't matter much in the enclosed spaces of the base game, in some custom levels favoring open spaces, this can get very annoying.
  • Container Maze: The first room of E2M2: Containment Area in the first Doom is basically a maze of crates with UAC supplies.
  • Continuity Reboot: Happened twice. Doom 3 and its expansion Resurrection of Evil does not descend from the events of Doom and Hell on Earth and the 2016 game is another reboot that does not follow on from 3. Eternal subverts this by revealing that it and 2016 are Stealth Sequels. It also implies 3 fits in somewhere.
  • Contractual Boss Immunity: Cyberdemons and Spider Masterminds are immune to splash damage. They only take damage from the rocket itself, not the explosion.
  • Covers Always Lie: The cover of the first game shows the Marine wielding what seems to be some kind of sub machine gun or small assault rifle, despite the game having no such weapon. It did, however, exist in the alpha — but that weapon was turned into a chaingun during development. It eventually made its way into Doom 3, albeit with a redesigned appearance.
  • Cruel Twist Ending: The ending to the original game — not counting the levels featured in "Thy Flesh Consumed" — suggests that everything will be fine for the Doomguy when he gets back home... Only for it to turn out that the Demons have invaded the Earth itself. And then they killed his pet rabbit, Daisy.

  • Damage Discrimination: With the exception of bullets, monsters are immune to their own kind's projectile attacks.
  • Damage-Sponge Boss:
    • Cyberdemons and Spider Masterminds.
    • Although they weren't bosses (except for the 'Bruiser Brothers' at the end of the first episode) Barons of Hell were considered to have hit points WELL out of proportion with their actual threat level. This led to the introduction of Hell Knights in Doom II, which were about as dangerous (their plasma orbs and claw attacks did the same damage), but only half as tough.
  • Darker and Edgier: The PlayStation and Saturn versions of Doom introduced darker music, colored lighting to give the levels a more foreboding feel, and revoicing the demons to appear far more intimidating.
  • Dead Character Walking: Has such a bug, described in detail here, where a players killed in deathmatch becomes a mobile corpse which runs (okay, slides) around. Kinda creepy.
  • Dead-End Room: The exit chamber of MAP12, though it doesn't prevent you going forward, it only prevents you re-entering the rest of the map. See also And I Must Scream above.
  • Dead Guy on Display: The demons really like hanging their victims from the walls and ceilings. The reason for this isn't explained, but most likely it is to scare off intruders (i.e you) and/or as snacks for later.
  • Deadly Dodging: A major tactic is to slip between enemies (or at least ensure one is between your attacker). If one enemy damages another with a ranged attack or barrel explosion, this results in monster in-fighting (generally resulting in one of the enemies dying.)
  • Descending Ceiling: There are two versions, both doing the same damage over time. The "slow" descending traps the player by slowing down the crushing process, while the fast one does a quick crush and raise. Also during the crushing phase, the player can't move because the ceiling is too low. Both of these are introduced in E2M4, the "slow" crusher having blood splatters on the ground, while the fast crusher being a surprise trap covering the key.
  • Deliberately Monochrome: The inviciblility powerup turns everything black and white while active, most likely so it's obvious when it wears off.
  • Diagonal Speed Boost: Strafing and running forward simultaneously is faster than doing either independently.
  • Difficult, but Awesome: The BFG9000 is actually a very tricky and unintuitive weapon to use to its full potential. The average player thinks it just shoots a big plasma ball that explodes into a large radius of splash damage upon contact with something, but how it actually works is that after the ball hits something, 40 invisible hitscan tracers shoot out from the player in the direction the ball was shot. As a result, if you're just running around firing off the BFG without keeping track of where you are when the BFG hits, you can have those tracers fire off in a completely unintended direction and have a lot or even all those tracers miss (for example, you shoot the BFG, you circle strafe around the enemies you shot at, and when the ball hits something you're on the other side of the group from where you fired at, so now the tracers shoot behind you where no enemies are). If you're aware of how the BFG works and can keep your aim steady and position close enough after firing, you can ensure those tracers hit their mark and deal out some really ridiculous damage (the ball alone can do up to 800 damage and as little as just 100, but when all the tracers hit it can deal out over 3000 damage). For an example of the difference this can make, if you're just perpetually circle-strafing a Cyberdemon while shooting the BFG at it, it could take as much as 10 shots to take down if much of those tracers aren't hitting, but if you can keep your aim steady after firing and get in point-blank range to ensure all tracers hit, you'll take down the Cyberdemon in just 2 hits. Also the BFG has quite a bit of startup to it before firing, adding more to the difficulty of properly using it (against a Cyberdemon for example, if you want to land a point-blank shot, you have to begin firing a distance far enough away to dodge its rockets, and then between the rocket shots weave in to point-blank distance in time with the BFG's shot coming out, and then weave out immediately to avoid any successive rockets it fires).
  • Digitized Sprites: Many monsters were made from clay and then converted to sprites.
  • Do Not Run with a Gun: The player is the only entity in the original games able to fire and move at the same time. Some mods change this.
  • Doomy Dooms of Doom: Uh...
  • Door Jam: Many traps in the first game and Doom II locks you up in a room with an army of monsters to kill, with the switch to open the door again being very well hidden, behind all those monsters, or non-existent (which forces you to search for a new path in order to find your way back). Notably is the 8th level of Doom II, Tricks and Traps, where you're thrown into a small room full of Baron of Hell and the strongest boss in the game, the Cyberdemon.
  • Downer Ending: The unnamed marine in the first Doom succeeds in escaping Phobos, climbing down from Deimos and escaping Hell itself, only to find that the demon invasion has already taken hold on Earth, with billions being slaughtered. The End! (The Ultimate Doom's fourth episode and the sequel has you saving what's left of humanity and ends on a triumphant note, at least.) There's even a miniature downer ending in the first episode, where you're transported into a darkened, inescapable room full of demons, and it's lampshaded by the game-ending text. Thankfully, you survive to go on to the next episode.
  • Downloadable Content: The 2019 suite of Unity ports received an update that allows players to download curated mods for these games for free through, such as both halves of Final Doom for both games, SIGIL for Doom, and No Rest for the Living for Doom II with other mods added through content updates.
  • Drought Level of Doom:
    • "Hell Beneath", the first level of the new episode from The Ultimate Doom, is known as one of or the hardest level in the classic Dooms, due to the very little ammo and health that was on the map when playing UV difficulty. Even with the level's hidden rocket launcher, killing everything without having to use your fists is impossible unless you can bunch up the Barons at the end and spread enough splash damage across them with the few rockets you have. Plus since it's the start of the episode, players have to always Pistol start it. The Playstation/Saturn port would alleviate these issues by adding a couple medkits from the lower difficulties and replacing all the Barons with Hell Knights that required a lot less ammo to kill, while the lack of episodes in those ports meant players didn't have to Pistol start the level either.
    • In the Jaguar, Playstation, and Saturn ports of Doom 1 they have a new map called "Hell Keep" to replace the PC's original Hell Keep, and it's infamous for having very little ammo, where on Pistol start you can't kill everything on UV difficulty without using your fists and/or exploiting infighting. Since Doom 1 is played as a single long episode in those ports instead of the multi-episode structure it originally had, players do not need to Pistol start it and so can bring their ammo and weapons from previous maps to alleviate the issue, but those that choose to Pistol start it found surprising difficulty when these ports were known for being usually easier.
  • Dual Boss: The two Barons of Hell at the end of the first episode of the original game. They get a repeat in Doom 3.
  • Earn Your Happy Ending: After destroying Mars, venturing home to Earth to find that it's been taken over, saving the entirety of the human race, then venturing to hell and BLOWING HELL UP Doomguy deserves this whole-heartedly.
  • Easier Than Easy: While it's not immediately obvious to the player, "Hey, not too rough" (the second difficulty) is the one internally labeled "sk_easy". "I'm too young to die" (internally "sk_baby") uses the exact same thing placements, but gives the player double ammo and halves their damage taken.
  • Empty Room Until the Trap: This series gets off on this. You'll probably run into a seemingly empty room, maybe containing some goodies, until you fall into a trap where a horde of demons await to destroy you.
  • Endless Corridor: Although the original Doom actually helped break first-person gaming out of the "straight corridor" mode, there are still many locations in the first game and its sequels where the endless corridor effect is invoked.
  • The End... Or Is It?: The text-crawl endings to the non-PC editions of the original all suggest that demons may have made it to Earth. The PC version makes it abundantly clear with the cutscene following the text that, yep, they did. And the Doomguy's pet bunny Daisy was their first victim.
  • Enemy Roll Call: Hell on Earth shows each enemy along with the name in the ending, but some of the names differ from those in the manual.
  • Epic Fail: What did the UAC want to do? Make teleporters. Result? Hell invades Earth.
  • Equipment-Based Progression: In the classic games, the player gets stronger as they find better and powerful weapons, and finding your first ammo backpack permanently gives you double the ammo capacity. Although the 2016 DOOM has stat upgrades for your suit, the weapons still have the spotlight and even exhibit the trope themselves with the mod system.
  • Escaped from Hell: The Marine dies at the end of the first episode. Three episodes later, he finds a portal back to Earth as the ending text says he was "too tough for Hell to contain".
  • Evil Is Not a Toy: The UAC teleporting things around seems perfectly sound until you realize that to do this, they had to lay their lines through Hell. Hell's demons, none too pleased at their domain being reduced to an interstellar railway system for a bunch of worthless humans, decide to jump into the transport system and pay what's waiting at the other end a visit.
  • Evil Is Not Well-Lit: The Playstation and Saturn versions utilize colored lighting and shadows to give the levels a darker, gloomier feel.
  • Evil Tainted the Place: The first episode's levels are your standard sci-fi military installations and science facilities. The second episode's levels have more hellish influences creeping in, with demonic symbols appearing on walls and pillars, electronics suddenly giving way to wood and stone, rivers of blood and lava, gnarled vines growing on walls, and a blood-red sky. It turns out that Deimos has actually been transported to the skies above Hell.
  • Evil Versus Evil: You can set up scenarios like this quite easily, and some demon types, such as Cacodemons and Barons of Hell, actively despise each other.
  • Evolutionary Retcon: Practically every memorable demon in the series was completely redesigned for Doom 3. Most of these redesigns made the demons appear much scarier and more formidable opponents for the player. The original imp, for example, was a large, brown creature with spikes on its shoulders that would slowly advance towards the player while hurling fireballs at them. The new imp is a slimmer grey creature with no spikes and ten eyes on its head that is capable of climbing walls and has incredible jumping ability that allows it to clear the distance across an entire room in a single leap and generally attacks with a much more aggressive style.
    • Then it goes full circle in DOOM (2016), where the enemies were redesigned to look more closer to their originals, and then redesigned again to be even more authentic in DOOM Eternal.
  • Excuse Plot: Demons have invaded Phobos/Earth/Mars! Go kill them all in an over the top and gory fashion.
    The Spoony Experiment: They tried to apply characters and a plot to this? It's DOOM! People play DOOM to get away from talking.
  • Expansion Pack:
    • The Ultimate Doom was a re-release of Doom featuring an additional episode.
    • There were also a series of unofficial commercial expansions. The original Doom had The Lost Episodes of Doom, which was originally sold with the book of the same name in 1995 and it came with a floppy disc containing a collection of three eight-level episodes. This expansion was originally made for the original Doom (v1.2-v1.9), not The Ultimate Doom, which caused some bugs and crashes to occur unless a patch was used for The Ultimate Doom.
  • Expressive Health Bar: The heads-up display includes a picture of the character's head. As the character takes damage, the head looks more and more hurt (bloodied and bruised). When the character has almost no health left, the head looks almost dead. If the character picks up the Invincibility Power-Up, the portrait will display Glowing Eyes of Doom. Receiving damage will cause the character to grit his teeth in pain, or (in certain version of the game) make a shocked face.

  • Fake Difficulty: The SNES port removed the ability to circle-strafe, making bigger enemies much harder to quickly defeat.
  • Fan Remake: The PlayStation version of Doom has a total conversion on PC (requiring GZDoom) with some enhancements and side mods to recreate the feel of the original game.
  • Five-Second Foreshadowing: Per word of John Romero, the first dead body you come across in "At Doom's Gate" isn't just there to establish the mood; it's meant to be a clue that there are enemies just beyond the door its near.
  • From Zero to Hero: The backstory of the game is that the Marine was sent to Mars as a punishment posting, watching the researchers of the United Aerospace Corporation do science-y stuff. Once things get dicey with the UAC's dimensional teleporters, the Marines head to Phobos to check on things. A Space Marine Is You gets left behind to guard the shuttlecraft with only a pistol while the rest of the squad goes in for a looksee. After some gunfire and screaming, the radio goes silent. The lone Marine must now fight his way through hordes of hellspawn to get back home. "Hell at last plays fair ..."
  • Fun with Acronyms: In the 2019 Unity port version of the Back to Saturn X series, the mod's title was changed to simply BTSXnote  while using joke subtitles for their respective episodes with Better Texturing with Startan X for Episode 1 and "Big Towers", says Xaser for Episode 2.
  • Game-Breaking Bug:
    • The PlayStation version has a TEXTURE CACHE OVERFLOW bug that crashes the game due to overloading the system's memory (especially on first-generation PlayStations) when a very large number of enemies are present.
    • Another PS1 bug that broke the game for anyone attempting to finish a level with 100% kills would sometimes occur if a monster was impacted by splash damage or was simply shot at when too close to a wall. The monster (this tended to happen most with the Lost Soul floating skull or any of the zombie soldiers) could be sent into the wall. The monster would still be visible and still in fact attempt to shoot or attack the player, but would otherwise be unkillable (and unable to harm the player). Adding to the surreal nature of the bug, the monsters would then start moving off into the distance until they effectively vanished from view (but could still be seen using the show monsters map cheat). This glitch appears to be unique to Doom proper and not the PS1-exclusive Final Doom sequel.
    • The "all ghosts" bug, also known as "intercepts overflow", causes many aspects of collision to completely stop working if a hitscan weapon has to make more than 147 collision checks. This can be (relatively) easily performed in the Icon of Sin, by hiding in a corner and letting the Mook Maker boss spawn enemies for over two hours until there's a pile of corpses high enough to trigger the bug, but it can also randomly occur in any level with any shot due to a rounding error which, if it happens at the right/wrong time, can cause the game to overpopulate the intercept list with many copies of the same few intercepts. Thankfully for casual players, the rounding error is already extremely rare, and the timing requirement makes actually triggering the bug rarer still — and even if the stars do align and the bug is triggered after all, saving and reloading fixes it. It does ruin mostnote  speedrun attempts, though, since loading is not allowed while recording demos.
  • Game Mod:
    • A large portion of Doom's appeal comes from its highly moddable nature, which Word of Godinvoked confirms is by design, building on the strong community response to map-making for Wolfenstein 3D, and desiring to make custom content creation more accessible (as well as to ease internal development)—game assets can be easily swapped with fan-made ones. The game engine's modular nature also means that Doom and Doom II are technically game mods themselves.
    • The source code for the game engine that powers Doom and Doom II, best known as the "Doom engine" (though officially known as "idTech 1" after id started making more game engines) was first released in 1997, then re-released under the open-source GNU GPL in 1999, then under the MIT License in 2014, which not only permits porting the game to just about anything with a CPU, controls, and a display, but also gives an entirely new depth of game modding potential that allows for deep-level modification of the engine to completely reforge it. This has resulted in Doom having one of the most wildly varied modding communities, with some of the higher-quality mods making Doom look utterly unrecognizable, as well as the "It Runs Doom" meme, referencing the fact that Doom has been ported to a huge variety of electronic devices, including several that were not designed to run video games in the first place.
    • Nearly three decades after the initial release of Doom, new mods, map packs, and total conversions are still being made. TV Tropes has a partial list of game mods that run on the Doom engine here. Many more mods can be found at the /idgames archive or at the numerous message boards which are still fairly active. Another alternative would be to use a modern server browser, which comes with an auto-downloader.
  • Gatling Good: The Chaingun. It's been a series staple and can mow down most enemies in seconds. The only time it becomes ineffective is against bosses. Despite its threatening appearance, though, its fire rate and behavior is more akin to an assault rifle; in Strife (another Doom-engine game released a few years later), the weapon is even redrawn into a rifle, and behaves convincingly enough.
  • Glass Cannon:
    • Pinky Demons and Spectres on Nightmare difficulty move at twice the speed, as well as attack at twice the speed, giving them the ability to attack very quickly with their bite that does up to 40 damage per hit. However, they still have their low 150 HP, allowing them to be killed fairly quickly by anything but the Pistol.
    • The Marine himself is one; he moves incredibly faster than every enemy in the game and can outrun their non-hitscan attacks, while his weaponry is far more powerful than what the demons possess (for example, the aforementioned Revenant rocket is one of the most dangerous attacks any enemy possesses, yet it is a less effective and weaker attack than the Doom Guy's simple Shotgun, and outside the Spider Mastermind and Cyberdemon, enemies that possess a weapon the Doom Guy has have a strictly inferior version). However, the Marine only has 100 HP at base (even less than the aforementioned Pinky), and at max health and armor has the equivalent of 400 HP (which most higher demons exceed).
  • The Goomba: The zombie troopers, who have 20 HP (meaning even the fist can kill them in 2 hits) and wield nothing but a rifle with the same feeble stats as the player's noob pistol. But much worse accuracy. Because they're zombies. And they only remember they have a weapon at random intervals. Because they're zombies. And if by some miracle they manage to get their necrotised brain together long enough to score a hit, the damn bullet only takes a single digit of your hp. Intentionally getting killed by one is difficult. It might get bored and walk out of the room or injure an ally and fight to the death before it can finish you. Because they're zombies.
  • Gorn: One of the games of the 90s, alongside the likes of Mortal Kombat, that created the moral panic about violence in video games for a reason. The original alone had gory death animations for some of the enemies, like Barons of Hell splitting in half to show their entrails and spinal cord, excess damage to weaker enemies (and the player!) turns them into red slop on the floor, and the environments were often decked out in corpses and gore the further you got into the games. In the modern era it's nothing special (some of the imagery can be on the unsettling side but that's the worst of it, with the violence itself being relatively mild) but in its age it was a wave of controversy.
  • Gray Is Useless: Doom has the numbers 2 through 7 on the status bar that represent the various weapons Doomguy can use. Doomguy always starts a level with the pistol, #2, but must collect better weapons in his travels. These corresponding numbers will be in dull grey until Doomguy obtains that weapon, although he can collect the ammunition for it beforehand.
  • Guide Dang It!:
    • Some of the secret areas can reach this level. The Containment Area in Episode 2, for example, not only has a secret room within a secret room, but there's a secret passage within that secret room leading to another part of the stage, and there's another secret room within that secret passage. Those who are used to more linear, modern FPS games will also sometimes find difficulty in navigating most Doom maps, as they tend to include repeatedly moving through areas to acquire keycards and open locked doors.
    • The difference between blue and green armors isn't just the amount of armor points they give you. (200 & 100 respectively) The blue armor reduced damage taken by 50% while the green armor has a 33% reduction. However, the game lets you pick up a green armor if you have less than 100 armor points, when it's usually beneficial to use up your superior blue armor first.
    • The way the berserk power-up works counts as this: it's basically a black medkit that heals you to 100 health (unless your health is already higher) as well as massively increase your punch damage. The confusion comes from the duration: most players believe it only lasts until the red tint it gives your vision fades (about 20 seconds), but it actually lasts until you leave the level or die. The reason for this is likely because the designers realized that having your vision be tinted red for the rest of the level would be really annoying, but it's still pretty confusing and counterintuitive, especially since the manual itself claims the effect is time-based rather than until the level ends.
    • The way the BFG works takes some experimenting to figure out as it doesn't cause Splash Damage exactly like the Rocket Launcher. The way the blast field materializes is based upon which direction you're facing when you fire the weapon, and how close you are to a particular monster. At point blank range, a Cyberdemon will barely survive due to all of the invisible rays hitting them, but further away, some of the rays will miss or hit other monsters.
  • Guilt-Based Gaming: When the player attempts to exit, a humorous quit message is shown, mockingly trying to convince the player to stay and play some more.

  • Harder Than Hard: The aptly-named "Nightmare!" difficulty, the only setting where monsters you've killed will respawn several seconds after they die. The monsters also shoot more rapidly than on all the other difficulty levels. And cheat codes are disabled. The only good thing about it is that ammo pickups contain double the normal levels of ammo like on the easiest difficulty... and you will need it all.
    • "Nightmare!" difficulty wasn't even included in the earliest releases of the game. It's very hard in single player mode, but it's fine for co-op multiplayer games, which let the players respawn, too.
    • Bethesda added a new "Ultra-Violence+" difficulty to their re-releases of Doom and Doom II. Take basic Ultra-Violence, then toss in the additional multiplayer-only item and monster spawns, and enable fast monsters as in Nightmare difficulty. You will die a lot. On the bright side, you'll also get more weapons and ammo a lot earlier in the game.
  • Have a Nice Death: ZDoom-based source ports by default display various obituary messages in the heads-up display based on which monster or hazard killed the player, e.g. "Doomguy was splattered by a Cyberdemon." Some of the monsters have two obituary messages based on whether the monster that killed the player used a melee or ranged attack, e.g. "Doomguy was slashed by an Imp." for the claw-slash vs. "Doomguy was burned by an Imp." for the fireball.
  • Heart Container: Health and armor bonuses respectively can raise your health and armor past 100, though you cap at 200. Soulspheres gives you an extra 100 health, Megaarmors gives you 200 armor instantly.
  • Health/Damage Asymmetry: The demons have very high health but weak attacks, while Doomguy is much flimsier but able to deal ridiculous amounts of damage. The only case where a demon has offensive power on par with the player is the Cyberdemon — the big guy's rocket launcher is exactly the same as yours. Now let it sink in that the rocket launcher, while definitely powerful, is not your most devastating weapon.
  • Hell on Earth: How the original game ends. After literally going through Hell and returning to Earth, you find that Hell has followed you home.
  • Hellgate: Not in the traditional sense as the teleportation system that the demons of Hell hijacked was merely a UAC conduit that used Hell as a pass-through wormhole in order to move matter across great distances in trivial amounts of time. The demons simply interjected themselves in the conduit, like a living phone tap, and invaded at both endpoints.
  • Heroic Mime: Doomguy (with the exception of the Comic) doesn't seem to have a whole lot to say. This may be because there is nobody to talk to.
  • Hero-Tracking Failure: Enemies have no idea how to lead their shots, meaning they're helpless to a player circle-strafing around them. The FPS convention of using the mouse to aim began as pro-skills tactic for Doom — the default control scheme exclusively used the keyboard and made moving and aiming simultaneously almost impossible.
  • Highly Conspicuous Uniform: The Marines wear sensible fatigues, but their body armor comes in Day-Glo Lime Green and Peacock Blue.
  • Hitscan: All bullet-based weapons and the invisible part of the BFG's fire cycle in the first two games.
    • In some cases (particularly Nightmare difficulty) this can make zombiemen even worse than their tougher imp counterparts. At least with imps you get a chance to dodge the projectiles that get shot at you.
  • Holodeck Malfunction: The premise of the "Cleimos" WAD.
  • Hyperspace Arsenal: Where the hell is the Doomguy keeping all of those weapons? Not to mention the ammo; at the start of the game the player can hold 50 full-sized rockets, in addition to other ammunition and weapons. When you later find a backpack, you double your ammo carrying capacity. A hundred explosive warheads are rather impossible to fit inside a military grade backpack, and that is not accounting for your twenty kilos of bullets and five full boxes of buckshot. The novelization made an attempt to justify this by explaining that these were cutting-edge space age mini rockets about the size and shape of a "D" battery.
  • Hyperspace Is a Scary Place: Hell was stumbled upon through teleportation experiments.
  • Iconic Starter Equipment: Doomguy/Doom Slayer is always seen using one of three weapons: the starting Pistol, the (sometimes starting) Shotgun or the Super Shotgun, the (usually) first weapon he stumbles upon during the first levels of his games.
  • Idiosyncratic Difficulty Levels: The difficulties are split into three categories of "easy" difficulties, a "medium" one, and "hard" ones, which add more and tougher enemies as you go up. The manual also has explanations for them:
    • I'm Too Young To Die: "An easy romp through the playground. Not many monsters here. This is good when you're learning the controls." The player gets doubled ammo from pickups and takes half the damage from enemies.note 
    • Hey, Not Too Rough: "This is good when you know how it works, but you still panic too much. Panic is a bad thing when you're surrounded by evil." Same amount of monsters as ITYTD, but your ammo pickup rate and damage taken are normalized.
    • Hurt Me Plenty: "The demons are out in force and they'll take great pleasure in hurting you as much as you let them." The middle difficulty, adding more monster spawns to the levels and/or replacing some spawns with tougher enemies.
    • Ultra-Violence: "So you think you're tough? Prove it!" Even more enemy spawns are added.
    • The v1.2 patch added NIGHTMARE!: "This is for those times where killing a guy once just isn't enough. If you're lucky, you'll wake up..." Same enemy spawns as Ultra-Violence, but now they move and attack faster, respawn shortly after dying, and cheats (except for level-warping and giving yourself the effects of a computer area map) are disabled. The game even gives a second prompt when you try to select it asking if you're sure and admitting that "this skill level isn't even remotely fair". You at least get doubled ammo like on ITYTD, because you're gonna need it.
    • The 2019 Unity ports added Ultra-Violence+: same as regular Ultra-Violence, but with the turbo enemies from Nightmare as well as things which normally only spawn in co-op modes appearing.
  • Idiosyncratic Wipes: The classic screen melt effect in every transition from the original. Some source ports add some extra wipes.
  • Imperial Stormtrooper Marksmanship Academy: Enforced with the Partial Invisibility power-up. Enemies can still see you (at least once you give yourself away by shooting), but since it implies that they can only tell the general area you're in, it drastically reduces enemy accuracy and causes them to fire wildly in your vicinity.
  • Insurmountable Waist-Height Fence: Central to much of the level design of the first two games, which did not feature any kind of jumping. Later source ports added jumping, allowing players to skip huge swaths of the classic levels by simply hopping over these obstacles.
  • Interquel: The Ultimate Doom, which was published after Doom II, contains a fourth episode for the original Doom, which occurs between the end of the third chapter of Doom and the beginning of Doom II.
  • In the End, You Are on Your Own: In the first game, the Doomguy is the Sole Survivor of the demonic invasion from Hell on the Martian moon bases. All the other humans have either been killed or zombified.
  • In the Style of...: Bobby Prince's music for the game is based on heavy metal — John Romero lent Prince a set of metal CDs for reference, and thus the soundtrack is filled with Suspiciously Similar Songs.
  • Jump Physics: You can't jump, but you can fall fifty feet without getting hurt.
  • Kaizo Trap: Halls of the Damned has a fake exit switch that instead dumps you into a room with a Cacodemon and a ton of Zombiemen.
  • Kill Enemies to Open:
    • "Phobos Anomaly" (E1M8) requires you to kill both of the Barons of Hell to lower the star shaped walls in their arena, which reveals a large courtyard with the teleporter to the exit.
    • "Against Thee Wickedly" (E4M6) has a particular nasty example where a Cyberdemon shows up near the barred off exit. The only way to raise said bars is to actually kill the Cyberdemon, and the space you have to fight him is generally very small, so good luck.
  • Kill the Lights: Picking up the blue key in the third map of the first game extinguishes all the lights in the room, and opens a Monster Closet full of imps. The imps are as accurate with their fireballs as ever; the player character, not so much.
  • Kubrick Stare: In Parts 1 & 2, as Doomguy takes more damage, his head dips lower and lower, producing this effect.
  • Lethal Joke Weapon: If you pick up a Berserk Pack, then your fists become this (but only to the more weaker enemies). After picking up the said powerup, your fist attack becomes more powerful and has the ability to actually splatter zombies and imps. Also, the "Berserk Fist" attacks are strong enough to interrupt a demon/spectre's biting attack and even kill them in 1-2 punches.
  • Level-Map Display: You can always look at a map of what you've explored so far. If you find a computer map, you can see the entire level.
    • Except in E1M8. Here the computer map is given to you right from the beginning. The level is named "Phobos Anomaly", but the map does not show the anomaly itself...
  • Lightning Bruiser: Cyberdemons are one of the fastest enemies in the game both movement and attack/projectile speed wise, while having significantly more HP than every other enemy in the game with a massive 4000 alongside a low pain chance and complete immunity to splash damage, and their rockets are just as strong as a player's, meaning they can kill you in one-two direct hits and easily lay waste to every other enemy in the game except the Spiderdemon in close quarters.
  • Literary Allusion Title:
    • The name Doom was chosen as a Shout-Out to Tom Cruise's pool cue in The Color of Money. (No, really.)
    • Episode 3 ("Inferno!") and its levels are named after Part 1 of Dante's The Divine Comedy.
    • As noted above, Episode 4 ("Thy Flesh Consumed") and its levels are named after Biblical passages.
  • Logic Bomb: In early versions of the classic games, monsters can fight each other if they hit each other. But if they somehow hit themselves (typically via barrels, as detailed in this article), they will tear themselves apart.
  • Ludicrous Gibs: Dealing enough damage will make certain monsters burst into red splatters.
  • Maybe Magic, Maybe Mundane: The original two games are somewhat ambiguous as to whether the demons are really demons from hell or just aliens from another dimension who happen to look like demons from Judeo/Christian mythology (indeed, they are even referred to as "aliens" in some of the text crawls and the book series explicitly says they are really aliens). Doom 3 and the 2016 Doom outright state they are demons from hell.
  • Make Way for the New Villains: For the first two episodes of Doom, the Barons of Hell are easily the biggest, baddest and toughest demons you go up against, and starting with their introduction at the end of episode 1, you fear them and know they're a force to be reckoned with. Then you reach "Tower of Babel", the final map of episode 2, and find yourself in a room with four Barons... all dead, horribly mutilated and strung up on the walls. If these were the biggest, scariest enemies in the game, what in the world did this to them? Then you meet the Cyberdemon. While Barons do still show up later in the games, this moment makes it abundantly clear that they're hardly the nastiest things you'll have to face.
  • Marathon Level: Going by the "par time" at the end of the levels, E2M4 and M6 are six and four minutes respectively, while it usually never goes to three minutes. Most maps on Episode 3: Inferno are really long and convoluted as well.
  • Meaningful Name: The third episode of Doom (Inferno!) draws its name and its episode names from The Divine Comedy. The fourth episode (Thy Flesh Consumed), and its levels except the secret level (Fear), draw their names from Bible quotations.
  • Mega-Corp: The Union Aerospace Corporation (UAC), a large government contracting firm that operates on the moons of Mars. While initially they have no harmful intentions, they have been screwing around by using Hell as a pseudo-wormhole in order to teleport things between their Phobos and Deimos bases. This, predictably, Goes Horribly Wrong and demons begin pouring out of the teleporters at Phobos while Deimos just disappears entirely. Later games give them a more insidious slant (particularly the 2016 game, which sees them using Hell as an energy source and Samuel Hayden trying to downplay the UAC's complete disregard for potential consequences, while another faction of the corp is an out and out demon cult led by the Big Bad).
  • Monster Closet: The Trope Codifier, along with Teleporting Keycard Squad. Often times rooms would be just a pedestal with an item on them, but taking the item opens up all the walls to reveal nasties. If you see a key or very good item, expect the baddies to pop out as soon as you get it.
  • Moral Guardians: Along with Grand Theft Auto and Carmageddon, this was one of the go-to scapegoats for grandstanding politicians for nearly a decade. The fact that Columbine shooter Eric Harris was revealed to play it certainly didn't help matters (not only that, but he made a Doom WAD of his own called UAC Labs, which made it onto DoomWorld's Top 10 Infamous WADs list).
  • Multi-Mook Melee: Many of the custom "slaughter maps" and Nintendo Hard megawads are mostly made up of these, with some fights in the infamous Deus Vult map (maps 1-4 are parts of the main map, which is map05) or the ever fun "Go 2 It", which involves a brawl against several Arachnotrons and Cyberdemons. The infamous nuts.wad has so many enemies note  that on badly coded ports framerate slows down to a crawl, even if using a computer made 20 years after the original game. However, serious maps with that many monsters have also been made.
  • Nerf: In the PlayStation port of Doom, Revenants were nerfed considerably, having the speed of their movement and punches/missiles reduced by about half. Though in some compensation, they only fire homing missiles instead of mixing them in with straight shots.
    • The player's Plasma Rifle also had its firing speed reduced by about half here, though it remained useful and able to reliably stunlock anything but a Baron and the bosses to death.
  • Nigh-Invulnerability: Due to how it's programmed, the iddqd cheat only makes you this rather than the complete invulnerability later games with a similar cheat would grant. The cheat makes the Doomguy invulnerable to anything that deals less than one-thousand points of damage, meaning there's only two things in the unmodified games that can kill him in that state: telefrags, since they deal ten thousand points of damage (this is normally not a problem since monsters are programmed specifically to be unable to teleport in if the player is occupying their destination, though the spawn cubes of Doom II's MAP30 and voodoo doll shenanigans where one telefrags oneself are exempt), and the type of damaging floor used at the end of Doom E1M8, which is programmed to nullify god mode (since being damaged to below 11 health by that floor is how ending the level is triggered).
  • Nintendo Hard:
  • No Fair Cheating: Using "-turbo" prints a chat message from time to time. In the original, and most ports of it, cheat codes are disabled entirely in Nightmare difficulty.
  • Non-Indicative Name: In Doom 2, the first level set in Hell is called "Nirvana", even though Nirvana is basically the Buddhist Heaven, making it a rather odd choice of name.
  • Nothing Exciting Ever Happens Here: The basis for the original game, being the marine's Antarctic reassignment following his incident with his superiors. Sent to Mars to simply keep him out of sight and out of mind, he happens to be in the right place at the right time when things go south.
  • Not Afraid of Hell: Doomguy. Hell is afraid of him.
  • Novelization: Four books based off Doom and Doom II (with the first two being actual novelisations of the game's storyline, such as it was). And two more based off Doom 3.
  • Nuclear Candle: The actual effect of the Light Amplification Visor is to brighten the whole map to max level.
  • Number of the Beast:
    • The version of Doom released to coincide with the original release of Doom II is v1.666.
    • The first map of Knee-Deep In The Dead has 666 linedefs in The Ultimate Doom.
    • The original Doom engine used port 666 for its multiplayer.

  • Oddball in the Series: The two Doom RPG games for being RPGs in a shooter series.
  • Oh, Crap!: If Doomguy is hit by a particularly strong attack and survives it, such as a Cyberdemon's rocket, he's supposed to make this expression. It doesn't quite work as intended in the original release, however.note 
  • One-Man Army: This may be the current benchmark. Did we mention that he blows up Hell by himself?!
  • One-Word Title
  • The Only One: You play the lone space marine who was left on guard duty at the ship, now the only thing standing against the hordes of hell.
  • Our Imps Are Different: Imps are the most common demons Doomguy will encounter; they typically resemble lean humanoids covered in spikes or bony armor. Their primary weapons are fireballs at long range and their claws at close range. Beginning with Doom 3, they can also use their claws to climb on walls and objects. They're the lowest on the demon totem pole, with only former humans being lower; in combat, they're Fragile Speedsters who rely on mobility and agility to make up for their physical fragility.
  • Our Zombies Are Different: The zombies in this game are very humanlike, to the point where they wield guns instead of shambling with their bare mitts like your typical living dead.
  • Overdrawn at the Blood Bank: Doom was one of the few video games in the early '90s that demonstrates that 2D sprites can spill lots of blood shot and killed, and some enemies can be gibbed when killed by high-powered weapons.
  • Painfully Slow Projectile: Most monsters' projectile attacks move very slowly. Unless you're playing on Nightmare difficulty, where several enemy projectiles move at double speed.
    • The BFG-9000, no matter the incarnation. In Doom 3, they travel so slow that you can literally shoot them out of the air before they hit you! This is, in fact, how you're supposed to defeat Sabaoth.
    • Averted with the Cyberdemon, whose rockets are just as fast as yours.
    • Also averted with Arachnotrons, whose plasma bolts are both fast and rapid-firing (although only about half the rate of your own Plasma Rifle). This makes them hard to deal with if you don't have space to move.
  • Password Save: In the PlayStation and Saturn versions of Doom.
  • Path of Greatest Resistance: If a room is filled with bodies, you've already been there.
  • Plot Coupon: The Blue, Yellow, and Red keys, when playing in single player mode.
  • Physical Hell: Doom's entire plot revolves around the idea that teleportation experiments on Mars resulted in portals to Hell itself, cue The Marine.
  • Popcultural Osmosis: The Imps use stock camel sound effects.
  • Possessing a Dead Body: The Former Humans are of this variety. They were Marines killed by the demons, which then took possession of their fallen bodies.
  • Psychotic Smirk: The marine is rather passionate about battling Hell's hordes as, after a new weapon is picked up, the protagonist grins devilishly at the prospect of blowing away demonic forces with it. The effect is magnified if the face in the HUD is bloody from taking damage.
  • Punny Name: Several songs on the soundtrack, including but not limited to Kitchen Ace (And Taking Names) and Nobody Told Me About Id.
  • Quad Damage: The Berserk Pack multiplies fist damage by ten times. For the rest of the level. You can gib weak mooks by punching them.
    • There's a (hopefully) intentionally crappy mod out there called All Hell is Breaking Loose! Among such things as flying demons that shout "Fuck you!" and flip you off when they die, the zombie soldier gib animation is replaced with them burning to death. This means that you can set someone on fire with a punch.

  • Random Number God: Not all weapons do the same consistent damage. While some may say that Berserk Punch has a heavy gap of damage (20-200 per punch), the biggest offender is the Unmaker (10-150 damage per shot). That 1 Unmaker laser shot can possibly not kill a Zombieman (weakest enemy in the game with 20 HP), but can sometimes kill a Demon (150 HP) in 1 hit. To compare in rare cases, 1 rocket launcher shot directly at a Demon may not kill it due to dealing 148 damage at lowest. So, yes, "What the !@#%* is this!" indeed. this video explains more about how the random number generator works, along with how you can use a hex editor to, say, make weapons always do maximum damage, or make the Icon Of Sin only ever spawn one kind of monster.
  • Rated M for Manly: Admit it, you've always wanted to kill demons with your bare hands.
  • Reassigned to Antarctica: The Doomguy in the original two games assaulted a superior officer who ordered him to fire on civilians. Rather than a court martial that would make them look like monsters if the reason for it got out, they decided to assign him to Mars — a barren rock whose only notable features were scientific outposts on its moons, and which was never expected to see any sort of action.
  • Red Shirt: The instruction manual explains that Doomguy didn't come alone to Phobos- he arrived with a whole team of marines, who entered the base to investigate while he guarded the perimeter. The demons have already killed them all by the time the game begins; you can find their corpses strewn about the first level.
  • Ret-Canon: The Doomguy in the cellphone-only Doom RPG series is related to B.J. from Wolfenstein 3-D.
  • Road Runner PC: The Doom marine was intentionally faster than normal monster movement, and could be made faster with a command line option. What wasn't intentional was strafe-running (+40% speed boost), and wall hugging (massive speed boost).
  • Roaring Rampage of Revenge: At the end of episode 4 in The Ultimate Doom it is revealed that the Doomguy's reason for killing all the demons was to avenge his pet rabbit Daisy, whose head you see on a spike at the end of episode 3
  • Rocket Jump: Ur-Example in first-person shooters. There's no vertical lift, but it does toss you around. One secret was specifically designed to require a rocketjump... though it can be reached just by straferunning.
  • Scenery Porn:
    • Try playing a map pack that requires a limit-removing source port and you're bound to get one of these. With the removal of the vanilla engine's notoriously strict mapping limitations, one of which closes the game entirely if exceeded, map creators became free to add extensive details to the architecture as well as huge sprawling open areas in their maps, resulting in stunning scenery if executed properly.
    • The Back to Saturn X series has gorgeous maps and impressive detail... designed to run under the vanilla engine, within its mapping limits as noted above. The trickery used to make bridges appear 3D as well texture cheats to create the illusion of sloped or curved arches are incredible.
  • Schizophrenic Difficulty: Episode 4 of The Ultimate Doom suffers from this. The level progression goes like this: starts out really hard -> ungodly difficult -> not as hard -> pretty easy -> about medium -> really difficult again -> somewhat easy -> ends on a rather medium difficulty level.
  • Secret Level: The Playstation 1 port of the original Doom contained two secret levels that remain exclusive to this version of the game: "The Mansion" - a confusing building-maze - and "Club Doom", accessible only from within "The Mansion" which featured (among other things) Revenants dancing in go-go cages!
  • Sensory Abuse: An infamous genre of WAD, referred to as Terry WADs after the troll who made the first examples, are built on this. These WADs play like normal until you activate a certain switch or linedef, at which point you're bombarded with ear-splitting noises, flashing lights, and text that describes anally raping the reader.
  • Sequence Breaking:
    • Straferunning is just one example of sequence-breaking tricks.
    • Jumping isn't possible in the original Doom, but many later source ports allow it. On some maps, this makes it possible for the player to jump onto platforms they aren't supposed to be able to reach yet (or even at all).
  • Set a Mook to Kill a Mook: A vital survival technique in the classic Dooms, especially in levels with more monsters than you can shake a boomstick at. If an enemy damages another enemy in any way, they will engage each other to the death unless angered by the player or a different foe. Infighting has some rules to it, such as monsters of the same type cannot damage each other with their projectiles unless they use a hitscan weapon, and when a monster is damaged, they'll have a randomised "targeting threshold", i.e. a period of time where they'll ignore damage from the player/other monsters while engaging the player/another monster they were initially damaged by.
    • Some of the levels even outright encouraged the player to exploit through design, some examples of which:
      • The first area of E3M1 didn't have enough ammunition to kill all the Beef Gates. It was punch them to death, or get them fighting each other. Since Imps and Cacodemons both had ranged attacks, getting them to hit each other was relatively easy. Then the retaliation started...
      • E2M9, the secret level in the second episode, had two rooms. One with Barons of Hell, the other with Cacodemons. Again, the trick was to get them fighting each other, then maneuver for survival. (Lampshaded in the novels.)
    • Lost Souls behave differently with in-fighting; they will make at most one attack when damaged (but can still exchange blows), and then resume attacks on the player. This gives them a rather cute personality since it will frequently happen that one will accidentally charge into another, causing the victim to bite it back in retaliation and appearing to argue with each other before resuming their attack on the player.
  • Shareware:
    • One of the most well known examples, Doom is probably the one title above all others which destroyed forever the "shareware is shareware because it's nowhere near good enough to sell at retail" myth. It was the first shareware product ever to be reviewed in the main pages of British PC Format magazine, instead of being relegated to the shareware section.
    • Carmack has said in a 20th-anniversary interview that shareware was actually not such a great fit for Doom. Not because any problem with the strategy itself, but because the game was such an obvious generational leap forward in game technology at the time, it literally sold itself, without need of any marketing gimmicks.
  • Shoot the Medic First: In ZDoom, it is possible to create enemies that can resurrect fallen foes via Decorate. Death for these guys should be top priority.
  • Shoot the Shaggy Dog: The original screws you over twice:
    • First, after defeating the Barons of Hell in the final level of the first episode, the only way out is through the teleporter... which takes you to Hell, where you're immediately overwhelmed by monsters and die (the coding in that room ends the level once you reach 11 HP or lower). The debriefing text really drives it home: "Once you beat the big badasses and clean out the moon base, you're supposed to win, aren't you? Aren't you? Where's your fat reward and ticket home? What the Hell is this? It's not supposed to end this way!"
    • And of course, the end of episode three. The Space Marine escapes from Hell and returns to Earth... only to find that the demons he had been fighting have already invaded. Cue the sequel.
  • Short-Range Shotgun: The original pump-action shotgun has a modest spread which is entirely horizontal (i.e. the pellets all connect in a straight left-to-right line) that will allow a good amount of its 7 pellets to hit at long distances, to where it can even be used as an effective sniping weapon in a pinch.
    • The SNES port combined all seven pellets into one uber-slug, meaning it was even worse for crowd-control but game-breakingly effective as a predecessor to the Sniper Rifle.
  • Shout-Out:
    • On the source port side, ZDoom has the developer's console cheat "anubis". Typing it in and pressing enter results in every monster in the game fleeing at the sight of you. Why? Because the message displayed when you hit enter is QUAKE WITH FEAR. Typing "anubis" again and hitting enter deactivates the fear effect with the message "No more Ogre Armor".
    • In the film, Dwayne Johnson actually had to fight to keep the "BFG" reference. There's also Pinky (who gets chainsawed), a Hellknight, and Reaper saying "Hell on Earth".
    • Episode 4 of The Ultimate Doom and all the levels within, excluding the secret one, have names based on biblical verses.
    • E4M1 of The Ultimate Doom has the Nine Inch Nails logo inscribed in a secret area. This was however removed in the 2019 Unity ports to avoid trademark infringement.
    • The penultimate difficulty level is named "Ultra-Violence".
  • Sliding Scale Of Silliness Vs Seriousness: The first three games are generally pretty serious (Doom 3 more so), but have bouts of goofiness and Black Comedy here and there. DOOM (2016) and DOOM Eternal, in comparison, are much sillier, with tongue-in-cheek plots involving an Obviously Evil Mega-Corp fracking hell for resources, largely comedic codex entries, many cases of Ascended Meme, and some pretty out there easter eggs. Even the Doom Marine has his moments.
  • Smoldering Shoes: The Cyberdemon's death animation in the original series has it explode, leaving just its hooves.
  • A Space Marine Is You: Possibly the Ur-Example, although most of the cliches are only found in the backstory from the game manual.
  • Splash Damage: The always venerable rocket launcher, along with the classic Exploding Barrels. Interestingly, the BFG, the biggest gun in the game, does not deal blast damage in the traditional sense, though; it instead fires a cone of invisible beams (from the player, not the projectile) in the direction the main projectile was fired in when it hits anything.
  • Standard FPS Guns: Fists, Chainsaw, Pistol, Shotgun, Chaingun, Rocket Launcher, Plasma Rifle, BFG. Doom was very important in creating and popularizing this one.
  • Stationary Boss: The final boss of the map pack Plutonia II seemingly rises up from the abyss after you teleport into his arena, but then he just remains stationary for the actual battle afterwards. In fact, looking at the map in a map editor reveals the effect was faked all along by having the arena itself descend down to his level, and thus, he never moves at all.
  • Status-Buff Dispel: While a God Mode cheat exists, there also exists a damaging floor type that can nullify it: Type 11, first introduced at the end of E1M8: Phobos Anomaly. Type 11 damaging floors inflict 20% damage per second (split between health and armor, if the player has any) and end the level when the player's health is at 10% or below. Telefrags can also bypass God Mode to One-Hit Kill the player in MAP30 of any Doom II-based WAD.
  • Stealthy Mook: The Spectres are partially invisible versions of the pink Demons. This ability is not true invisibility (except in dark rooms) but is enough to trip up a player if they're not totally observant.
  • Stock Sound Effects: Almost everything, from the monster roars to the launch sound of the monster spawn cubes in MAP30, thanks to id licensing sound FX from the Sound Ideas library. This is why all, or nearly all, of the FX used in Doom sound familiar to movie buffs; they've been used in many movies and TV shows, both before Doom and since. In fact, one of the stock sounds is known today as Doom Doors.
  • Strange Secret Entrance: Some of hidden levels in the series are like this. For example, getting to one secret level required you to blow yourself off a ledge by firing your rocket launcher into a wall at point blank range.
  • Summon Bigger Fish: See Set a Mook to Kill a Mook above. If you can get powerful monsters to fight each other or mow down cannon fodder, you can save yourself a lot of trouble.
  • Supernatural Goldeyes: Picking up invincibility (or turning on God Mode) turns the Doomguy's eyes gold.
  • Super Title 64 Advance: The PlayStation port of Doom has the subtitle "Custom PlayStation Edition".
  • Surreal Horror: One thing that stays consistent throughout the franchise is that Hell is really Goddamn weird. The laws of physics as seen in our reality don't seem to apply most of the time, and the areas you're fighting through can suddenly shift into another shape entirely. Not to mention some of the surfaces being made of spinal columns and human faces.

  • Tactical Suicide Boss: Due to how enemies are coded to react to barrels exploding and hurting them, it is possible to trick the Barons that cap off the first episode into fighting one another, despite code designed to prevent this, by having one damage a barrel and then the other destroy it while the first Baron is within its blast radius. Early versions of the game were even worse, as the way the code worked meant that it was also possible to trick a Baron into infighting with itself via barrel, causing it to swipe at the air in random directions and literally tear itself apart.
  • Take That!: In "Grosse", four copies of the titular hero of Commander Keen are hung by a noose, with the player required to shoot them to get to the end of the level. John Romero stated that Adrian Carmack, who had worked on Commander Keen, hated the games and the character, and this was his way of getting even.
  • Take That, Audience!: The ending text for the PlayStation and Saturn ports tells the player they can "retire to a lifetime of frivolity".
  • Tank Controls:
    • Controlling the original game with just the keyboard or mouse defaults to this, though with the ability to strafe by holding a modifier key that changes your turning controls into strafing ones while it's held. Using both at once allows for separate turning and strafing.
    • Also the case for the SNES port; like the DOS original there's a button to read the turning controls as strafing, but it's impossible to turn and strafe at the same time in this version.
    • The default setting for the PlayStation and Saturn versions, as well. You can change the controls, although it's not very extensive.
  • Tele-Frag: Just like "frag", it was also first coined in Doom multiplayer matches. Some Doom levels allow you to telefrag monsters (e.g., E4M2 in The Ultimate Doom).
    • Telefrags also ignore whether the telefragged is invulnerable or not and just outright splats them. To be exact, "invulnerable" (whether by Power-Up or by God Mode cheat) means "immune to attacks scoring 1000 Hit Points or less of damage". A telefrag is the only source of damage to surpass that, doing 10,000 HP damage.
  • Teleporter Accident: A teleporter breaches hell in the backstory. The demons took notice and decided to pay humanity a "friendly visit".
  • Teleporting Keycard Squad: More often than not, you can expect to find a horde of demons swarming upon you when you pick up a keycard.
  • There Is No Kill Like Overkill: The "Russian Overkill" mod adds dozens of ludicrously-overpowered weapons (and some that are not quite so overpowered but are either funny, clever, or just plain bizarre) that effectively remove any challenge the game ever had. At least one weapon's alternate-fire mode can one-shot a Cyberdemon. To say that some of these guns can wipe out an entire level's monster population with a single round is, in many cases, barely an exaggeration.
  • This Looks Like a Job for Aquaman: Normally the Partial Invisibility powerup is a detriment, as the erratic randomized firing it causes in enemies makes their projectiles a lot more difficult to dodge as you can no longer anticipate where they fire. Against enemies with hitscan attacks however, as you can't dodge their attacks to begin with except by praying that they decide to miss, the erratic firing will cause them to miss you a lot more often and save you from a lot of otherwise unavoidable damage. As such, when against a large amount of hitscanners, especially Chaingunners, Partial Invisibility becomes immensely useful. note 
  • Trope Codifier: For the FPS genre. Until about 1998, they weren't even called "first-person shooters", but were instead "Doom clones".
    • The rude, manly space marine has become ubiquitous since then.
    • The "crate maze", as first seen in E2M2: Containment Area, has also become an FPS cliché. It originated as a good way to have a large area without overtaxing the engine.
  • To Hell and Back: Once per game. All of them one hell of a trip.
  • Unbroken First-Person Perspective: As with other classic shooters like Wolfenstein 3D, this game pre-dates the tendency to break up gameplay with cutscenes, so the entire game is from Doomguy's perspective. The only things that could be considered breaks in perspective are text screens appearing at the end of each episode, which are narrated to the player in Second-Person Narration.
  • Unexplained Recovery: At the end of the first game's first episode, you enter a teleporter that takes you to a pitch black room with a special damaging floor and many monsters. As soon as you are reduced to 10 health or less, the level abruptly ends, with the implication that you died. However, the end text itself remarks how you wake up in Deimos, alive and unharmed but weaponless. Since it turns out that the entire moon of Deimos has been pulled into Hell, a common explanation is that you died and were sent to Hell... but if that's the case, why would you have a pistol and 50 bullets when you first materialize?
    • The novelization by Dafydd ab Hugh and Brad Linaweaver says that Taggart (the Doomguy in this version) arrived naked and weaponless, but found some weaponry. Maybe something similar happened offscreen?
  • "Untitled" Title: The levels "Fortress of Mystery" (E2M9) and "Hell Keep" (E3M1) has the music track "Untitled", possibly because "MIDI Version of Mouth for War" was too cumbersome and litigation-prone.
  • Unintentionally Unwinnable: E2M4: In version 1.1, approaching the yellow key, retreating to a different room, and returning causes the crushing ceiling to be permanently lowered, sometimes blocking access to the key. That version forgot the original ceiling height whenever the crusher stopped.
  • Unwinnable by Design: It is absolutely impossible to properly complete E1M8 (Phobos Anomoly) like the other levels. Even if by some fluke of fate you are able to kill all of the enemies, the floor of the room you're teleported into is programmed to gradually damage you. On top of that, if you cheat to take no damage to get past the ambush and floor, theres no exit waiting for you, and there's no way to backtrack to the rest of the level either. In short, the only way to "beat" the level is to die at the very end.
  • Updated Re-release:
    • The Ultimate Doom added no new monsters or weapons (not even the new ones added in Doom II), but a new episode to the original game. It was basically an excuse to get Doom, formerly distributed as shareware, sold in retail stores.
    • The Xbox LIVE Arcade version of The Ultimate Doom and Doom II has updated graphics and music, and online multiplayer. These treatments were also added for PlayStation Network's Doom Classic Complete compilation.
    • The 2019 Doom Classic editions of Doom I and II for PlayStation 4, Xbox One, Nintendo Switch, and mobile devices, after multiple patches, features the ability to officially play these games in 60 FPS, added a new weapon wheel for weapon selection, split-screen multiplayer, and the ability to download curated and compatible mods from, among them being Final Doom, No Rest for the Living, and SIGIL at the comfort of your favorite console/handheld/PC. This version later made its way onto PC as well on and later Steam, with the ability to add in your mods like in the mobile version. Another update later added 16:9 widescreen presentation, variable frame-rate options for supported devices, toggleable V-sync, gyro aiming controls for Switch/PlayStation 4/PC with DualShock 4 controllers, a new Ultra-Violence+ difficulty, revamp the deathmatch multiplayer, and support for mods that uses DeHackEd.
  • Vague Hit Points: Enemies have Hit Points, as seen when looking at the source code, but there's no way to measure it in the regular game, instead the player can only remember how many hits of each weapon it takes to take down specific enemies.
  • Visible Invisibility: A weird example: The invisibility sphere (more accurately named "partial invisibility" in game) turns you into a sort of staticy looking outline. As such, you're not completely invisible to monsters - some may take a while to realize you're in front of them if you don't fire a weapon, and once a monster is aware of you they'll fire off projectiles in your general direction rather than directly at you. The weird part is that it doesn't prevent monsters from seeing you but just makes their aim worse, and has no effect on monsters with no ranged attacks.
  • The Walls Have Eyes: Some wall sprites have moving walls of faces staring at you, and in later episodes/levels of Doom the switches are now stone heads whose eyes glow when you hit them on. Other switches are just eyes protruding out of fleshy patches, closing when activated.
  • The War Sequence: Custom levels pitting the player against massive hordes of enemies (called "slaughter maps") are somewhat popular amongst the Doom community. The official Doom levels have a couple of their own as well, perhaps most (in)famously E4M2, "Perfect Hatred".
  • With This Herring: Hand waved in the first couple of Doom games, where you initially do battle with the legions of Hell while carrying a single pistol. This is explained by the Excuse Plot saying that you were a sentry stationed outside the base while everyone else went in to find out what happened. Naturally, all those people with the huge guns got killed and you're the only one left. This does not come off as being particularly convincing.
  • Your Head Asplode: In the PS1 and Sega Saturn versions when you get gibbed, the status bar face explodes rather than being all caved in and dead like a normal death. The 3DO version explodes the face no matter how you die.

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