Monsters found in The Ultimate Doom:
- Zombieman
- Shotgun Guy
- Imp
- Demon (Pinky)
- Spectre
- Lost Soul
- Cacodemon
- Baron of Hell
- Cyberdemon
- Spider Mastermind
Additional monsters found in Doom II (and Final Doom):
- Heavy Weapon Dude
- Revenant
- Hell Knight
- Arch-vile
- Arachnotron
- Mancubus
- Pain Elemental
- Icon of Sin
New monsters only found in the Legacy of Rust expansion: