Demonic monster, demon, the mortally challenged, and hellspawn, are the designations given to a collection of extradimensional species originated from Hell/Jekkad. Their ultimate goal is to destroy Earth and other dimensions.

Classic Doom games

Doom

Doom and its retail extension, The Ultimate Doom, include the following monsters:

• Baron of Hell - Two of these act as the boss in Knee-Deep in the Dead, resembling large pink Minotaurs or Satyrs. It can hurl streaming balls of green flame or energy and employs a powerful clawing attack at close range. They can take enormous punishment before being slain.
• Cacodemon - A large flying head-like monster with red scales, horns, and one eye. It moves relatively slowly, but has strong jaws and spits out "lightning balls" from a distance.
• Cyberdemon - The massive boss in The Shores of Hell, a monstrous humanoid cyborg as tall as two men that can absorb more damage than any other monster and moves at a relatively rapid rate for its size, pausing only to fire rockets from its mechanical arm at anything foolish enough to oppose it.
• Demon - About the size of a gorilla, this muscular pink brute runs quickly on its two hind legs to bite opponents. While not an immediate threat on their own, when in groups they do have a tendency to try and outflank their targets.
• Imp - A brown, human-sized humanoid demon that throws round fireballs and claws nearby opponents.
• Lost Soul - A floating, flaming skull that can rush quickly to gore an opponent.
• Spectre - Identical to the Demon, except that it is partially invisible.
• Spider Mastermind - The cybernetic boss in Inferno and Thy Flesh Consumed. It appears as an enormous brain with eyes, a mouth, and comparatively small arms, atop a four-legged metal chassis with an incorporated triple-strength chaingun which will mow down the unwary to bits within moments.

See also Player and Barrel.

Doom II

Doom II (and thus also Final Doom) includes the same monsters as Doom in addition to the following monsters:

• Arachnotron - Strongly resembles the Spiderdemon, but is much smaller, and shoots greenish plasma instead of super-chaingun rounds.
• Arch-vile - A peach-colored, emaciated humanoid demon who is quite tough for its size. It can summon fire, resurrect dead monsters and is the fastest monster in Doom II (almost one and a half times as fast as the Cyberdemon).
• Hell Knight - Identical to the Baron of Hell but tanned in color, emits higher-pitched sounds and endures only half as much damage.
• Icon of Sin - Though not technically a monster, it does still represent one of the protagonist's opponents. The principal one, to be exact, that must be defeated to win the game.
• Mancubus - A grotesquely bloated humanoid with flamethrowers instead of forearms. It moves slowly, but takes a fair amount of ordinance to bring down.
• Pain Elemental - A large flying head resembling a brown Cacodemon with small arms. It attacks by spitting Lost Souls at its target, and even creates a few more as it dies.
• Revenant - A tall, skeletal demon wearing silver body armor that can launch ballistic or guided missiles, and punch opponents when at close quarters. These are the results of recycled demon combatants.

Newer Doom franchise games

The newer games of the Doom franchise generally include a set of monsters from the PC Doom games or inspired on them and possibly a number of new creations. Various ports include the same sprites as their predecessors, although some change their appearances either to achieve a new style (such as in Doom 64) and the newer games (such as Doom 3) provide polygonal versions that suit their more advanced technology and rendering capabilities.

Doom RPG

Doom RPG features almost all of the monsters from Doom II, with the exception of the Shotgun Guy, Spectre, Arachnotron, Wolfenstein SS, Commander Keen and Spiderdemon (as well as the final boss). It includes the following unique monsters:

• Hellhound
• Kronos

Non-boss 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 and vary in difficulty.

Doom II RPG

The Doom RPG sequel Doom II RPG has almost the same enemy entity set as Doom RPG, but adds a few of its own, even adding a few boss entities. The game adds the following new enemy types:

• Chainsaw Goblins (Lesser Sawcubus, Greater Sawcubus, Chainstrosity)

In addition to the new classes of enemies, the game has two new boss class entities; the Pinkinator and VIOS. All the sprite artwork used for the enemies was hand-drawn specifically for this game--even for "classic" monsters returning from previous games in the series--in order to allow for higher-resolution sprites than what was used in the original Doom games (though the higher-resolution sprites are only used on higher-end devices).

Sony PlayStation

The official port of Doom to this platform removes the Arch-vile but includes an additional monster over the PC versions.

• Nightmare Spectre

Doom 64

Doom 64 includes newly illustrated versions of the Doom and Doom II monsters, created from high-poly rendered models rather than sculptures or hand-drawings. The Revenant, Heavy Weapon Dude, Arch-vile, Spiderdemon, Wolfenstein SS, Commander Keen and final boss are not present, but instead it features some new monsters:

• Mother Demon
• Nightmare Imp

Doom 3

Doom 3 includes its own versions of many monsters from the original games. Some of these, such as the Demon and the Hell Knight, are considerably different from their predecessors.

• Arch-vile
• Cacodemon
• Cyberdemon
• Demon
• Hell Knight
• Imp
• Lost Soul
• Mancubus
• Revenant

Additionally, the following new monsters are encountered:

• Cherub
• Guardian of Hell
  • Seeker
• Maggot
• Tick
• Trite
• Vagary
• Wraith

Some concepts of monsters, one of which resembles the spider-like monsters from Doom and Doom II, were shown by id Software during development of the game but did not make it to the finished product.

Doom 3: Resurrection of Evil

All the monsters in Doom 3 appear in Resurrection of Evil, except the Sabaoth, Vagary, Cyberdemon, Guardian, Seeker, and Lost Soul. Additionally, some new monsters are included:

• Bruiser
• Forgotten One
• Hell Hunter
  • Helltime Hunter
  • Berserk Hunter
  • Invulnerability Hunter
• Maledict
• Vulgar

Doom (2016)

The Doom reboot features a lot of returning monsters from the previous three games.

• Baron of Hell - Are larger than more agile than previous appearances, easily capable of outrunning the player.
• Cacodemon - Their attacks now blurs the players vision. If hit in the eye, they will spin around, shooting in random directions, and then die.
• Cyberdemon - A boss, with several new abilities, including a laser attack and a flame wall.
• Hell Knight - Resemble their Doom 3 incarnation, but can no longer throw fireballs. Instead they have increased speed and agility to chase and pummel the player.
• Imp - Far more agile, capable of climbing up walls and leaping over large gaps. Can also charge their fireballs into more powerful versions.
• Lost Soul - Now explode upon impact.
• Mancubus - Now covered in armor plating that protects their chests, and can launch their flames in streams rather than just fireballs.
• Pinky - Covered in thick armor on their faces and have a charging attack, making players have to dodge and attack their vulnerable tails. If the front armor is damaged enough, it will leave the face as weak as the back.
  • Spectre
• Revenant - Once again with shoulder mounted cannons, this demon now has the ability to perform short hops between platforms with its jetpack.
• Spiderdemon - Final boss, equipped with a plasma cannon, lasers, an electric attack and telekinesis.
• Summoner - They are similar to Arch-viles, but can float, travel at untouchable speeds, and have a revamped appearance.

It also includes some new monsters.

• Cyber-Mancubus - Mancubi with heavier armor, and shoot toxic slime rather than fire, at greater ranges.
• Gore Nest - Not technically demons, but an important part of fighting them. Gore Nests appear as objects to be destroyed to remove "demonic presence" from areas. Destroying them summons a wave of demons.
• Hell Guard - A trio of bosses, biomechanical suits inhabited by Parasites. They have various flame and energy-shield based attacks.
• Hell Razer - Similar to an upgraded Possessed Soldier, Hell Razers are demons with an arm cannon that fires a beam of Hell energy.

Multiplayer includes two new demons for players to play as.

• Harvester - A demon that absorbs life energy to fuel its attacks.
• Prowler - Demons similar to Imp, but stronger and without the fireballs.

Doom Eternal

This installment to the series returns almost all of the Doom (2016) monsters, all redesigned due to a software upgrade.

• Baron of Hell - Beefier than its past versions, but dwarfed by many other demons on this list.
  • Armored Baron - This demon's armor can be destroyed with the plasma rifle or by shooting its mace when green. Otherwise, it is just a stronger version of its namesake.
• Cacodemon - Now without the eye weakness, this demon flies faster, but is otherwise the same.
• Tyrant - This enemy can withstand a direct BFG shot.
• Hell Knight - This monster is more agile still than its past incarnations.
  • Dread Knight - A stronger version of the Hell Knight, it can use its flame blades to slash the air and throw a wave of fire at the player.
• Imp - Quite similar to its 2016 counterpart, the Imp is far more useful as fodder to clean up bigger enemies.
  • Stone Imp - Similar to the Imp, but resistant to all attacks except from the fully automatic shotgun or the sentinel hammer. It can also perform a high-speed rolling maneuver.
• Lost Soul - With improved flame effects, the Lost Soul is now fired by the returning Pain Elemental.
• Mancubus - Though it seems to be the same as its earlier incarnation, this demon's arm cannons can be shot off.
  • Cyber-Mancubus - Weaker than that from 2016, the Cyber-Mancubus' armor can be shot off. Its green flames cause lingering damage to the player.
• Pinky - Now with much-improved turning speed, it gets stunned for a couple seconds after charging into a wall.
  • Spectre - This demon is nearly invisible to the player, only revealed through frost grenades.
• Gore Nest - This works the same as last time, but the orb which the Slayer pulls out is more yellow.
• Prowler - The Prowler is much more powerful in this game, being able to teleport and throw purple energy balls.
  • Cursed Prowler - If this demon damages the player, it curses them so they slowly lose health and cannot lock on to enemies.
• Revenant - Quite similar to the one from 2016, this monster's shoulder cannons can now be shot off.

It has a few demons not in Doom 2016 but in other installments.

• Arachnotron - This demon has a head mounted turret which can be shot off. It fires grenades and plasma at the player, can climb on many surfaces, but is not too fast.
• Arch-vile - The Arch-vile can summon demons, control and attack with fire, teleport, and buff nearby monsters. However, it cannot reanimate dead demons like its previous versions.
• Pain Elemental - This monster fires Lost Souls at the player, and has a lot of health.
• Icon of Sin - Now an actual boss fight, this demon once again is huge and powerful. After its armor is shot off, it can be killed with the Crucible.
• Gargoyle - Like a weaker Revenant, this demon can perform short hops with its wings, but has the strength of an Imp and can be easily shot from the sky.
• Whiplash - Though not very tough, this monster can dodge many attacks from the Slayer, and must be killed while upright. It can damage the player from a distance with whips or through the ground.
  • Whiplash Spectre - Like the Whiplash, only weaker and invisible.
• Doom Hunter - This demon sits on tanks with cannons, and when the tank is shot off, it gains lots of speed but loses all attacks but melee.
• Gladiator - Extremely resilient, this demon has two maces and a shield, as well as diagonal projectiles which it hurls at the player.
• Tentacle - This ambient monster is weak, but if the player doesn't pay attention, it can cause a lot of damage when it pops out of the ground.
  • Giant Tentacle - Like the Tentacle, but much larger, much stronger, and slower.