Monster

In single-player and cooperative multiplayer games, much of a player's time is spent in combat with enemy monsters. The monsters are placed into the map by the level designer and remain dormant until activated. Monsters are activated when they see the player, when they sustain a damaging attack, or when they hear the player attack, even if this is with the (otherwise silent) punch.

When activated, monsters advance on the player and attack. Monsters can sense the location of the player even if the player is out of sight, and advance on that location even if it is on the other side of the map. If monsters hit an obstruction, they attempt to walk around it. Monsters remain activated indefinitely. However, there is a bug in Vanilla Doom which returns the monsters to a dormant state if the player saves and then re-loads the game.

In general, monsters of a different class can accidentally hurt each other, causing infighting. Monsters can use teleports, although they do so accidentally, as their artificial intelligence is very limited. Monsters can activate lifts and open certain doors, although certain monsters cannot fit through doors and openings that are just large enough for the player. Monsters can be hurt and killed by crushing ceilings, although they are unaffected by all forms of damaging floors.

Doom/Ultimate Doom

 * Former Human: Once a Marine like the player, now undead and carrying a rifle.
 * Former Human Sergeant: A more durable zombie with a shotgun.
 * Imp: A humanoid demon who throws small fireballs.
 * Demon: Slightly larger than a human, this pink creature runs forward on its two hind legs to bite the player.
 * Spectre: Almost identical to the Demon, but partially invisible.
 * Cacodemon: A large flying head with red scales, horns, and one eye. It moves relatively slowly, but has strong jaws and can fire lightning balls from a distance.
 * Lost Soul: A floating, flaming skull with a high-speed ramming attack.
 * Baron of Hell: The boss monster in Knee-Deep in the Dead, resembling a large minotaur. He can hurl bolts of green plasma, and employs a powerful clawing attack at close range.
 * Cyberdemon: The boss monster in The Shores of Hell. A hulking, humanoid cyborg of immense strength, he moves faster than any other monster in the original Doom (except from an attacking lost soul), pausing to fire volleys of rockets.
 * Spider Mastermind: The boss monster in Inferno and Thy Flesh Consumed. She appears as an enormous brain with eyes and a mouth, encased in a four-legged metal chassis, and packs a chaingun far more dangerous than the player's.

Doom II/Final Doom
All of the original Doom monsters, plus:
 * Former Human Commando: A tough, aggressive zombie with a chaingun.
 * Hell Knight: Has half as much health as the Baron, but looks very similar and fights in the same way.
 * Revenant: A tall, skeletal demon wearing armor. He can launch ballistic or guided missiles, and punch the player when in close quarters.
 * Mancubus: A grotesquely bloated humanoid with flamethrowers instead of forearms. Moves slowly, but takes a fair amount of ordnance to bring down.
 * Arachnotron: Strongly resembles the Spider Mastermind, but much smaller, and uses a plasma gun instead of a chaingun.
 * Pain Elemental: A large flying head with brown scales, horns, and one eye. It attacks by spitting Lost Souls toward its target, and even creates a few more as it dies.
 * Arch-Vile: A white, emaciated humanoid who moves rapidly and is quite tough for his size. He can cast spells to engulf the player in flames, and knows how to bring dead monsters back to life. He is the fastest monster in Doom II, being almost one and a half times faster than the Cyberdemon.
 * Icon of Sin: The giant, immobile boss monster at the end of each IWAD, who attacks by creating other monsters. He can be killed only by firing rockets through a small hole to hit the avatar inside.
 * Wolfenstein SS: Populates the two Wolfenstein-themed secret levels; not as dangerous as the original.
 * Commander Keen: A hanging effigy of the cosmonaut from id Software's pioneering series of games. He neither moves nor attacks.

Doom RPG
Doom RPG features almost all of the monsters from Doom II, with the exception of the Former Human Sergeant, Spectre, Arachnotron, Wolfenstein SS, Icon of Sin and Spider Mastermind. It includes the following unique monsters:


 * Hellhound
 * Kronos

Enemies in Doom RPG are organized into classes. For example, there are three types of Imps, while the Hell Knight and Baron of Hell both belong to the "Baron" class. Monsters in the same class use the same sprites but are somewhat differently colored.

Doom 64
All of the Doom II monsters, minus the Revenant, Chaingunner, Arch-Vile, Spider Mastermind, Wolfenstein SS and Icon of Sin, but including:


 * Nightmare Imp
 * Nightmare Spectre
 * Nightmare Cacodemon
 * Mother Demon

Doom 3
Of the monsters in Doom 3, some are new versions of monsters from the original games, while some are entirely new. Some of the old monsters, such as the Hell Knight and Demon, are very different from their predecessors.


 * Arch-Vile
 * Cacodemon
 * Cherub
 * Cyberdemon
 * Guardian
 * Seeker
 * Demon
 * Hell Knight
 * Imp
 * Lost Soul
 * Maggot
 * Mancubus
 * Revenant
 * Sabaoth
 * Tick
 * Trite
 * Vagary
 * Wraith
 * Zombie
 * Chainsaw Zombie
 * Fat Zombie
 * Flaming Zombie
 * Z-Sec Zombie
 * Zombie Commando

Doom 3: Resurrection of Evil
All the monsters in Doom 3 minus Sabaoth, Vagary, Cyberdemon, Guardian, Seeker and Lost Soul, plus:


 * Vulgar
 * Forgotten One
 * Bruiser
 * Hell Hunter
 * Helltime Hunter
 * Berserk Hunter
 * Invulnerability Hunter
 * Maledict
 * Bio-Suit Zombie

Doom movie
The Doom movie featured monsters from the series it was based on, but there were some differences between the video game and movie adaptions of the monsters.


 * Imp
 * Baron
 * Pinky

Heretic

 * Disciple Of D'Sparil
 * D'Sparil
 * Fire Gargoyle
 * Gargoyle
 * Golem
 * Golem Ghost
 * Green Chaos Serpent
 * Iron Lich
 * Maulotaur
 * Nitrogolem
 * Nitrogolem Ghost
 * Ophidian
 * Sabreclaw
 * Undead Warrior
 * Undead Warrior Ghost
 * Weredragon

Hexen

 * Affrit
 * Brown Chaos Serpent
 * Centaur
 * Dark Bishop
 * Death Wyvern
 * Ettin
 * Green Chaos Serpent
 * Heresiarch
 * Korax
 * Maulotaur
 * Menelkir
 * Reiver
 * Slaughtaur
 * Stalker
 * Stalker Boss
 * Traductus
 * Wendigo
 * Zedek

Enemies

 * Acolyte
 * Bishop
 * Ceiling Turret
 * Crusader
 * Entity
 * Inquisitor
 * Loremaster
 * Programmer
 * Reaver
 * Sentinel
 * Shadow Acolyte
 * Specters
 * Stalkers
 * Templar

NPCs

 * Governor Mourel
 * Macil
 * Rebel
 * Peasants
 * Armorer
 * Bar Keep
 * Becoming Acolyte
 * Beggars
 * Kneeling Guy
 * Medic
 * Oracle
 * Weapon Smith

Technical

 * Monster infighting

Background

 * Models