This is DustedPandemonic/Hecatia's Complex Doom addon.
The only requirements are LCA (and of course Complex Doom, and RM if you're using the patch).


Credits are listed below.

If credits aren't listed for something, that means that I was 
not able to find an author of the specific item (or I'm just lazy).

Tripwire Interactive: Gore Imp, Cerebral Caco, and Cerebral Imp sounds (Killing Floor)
Nakkemake: Old Desolator sprites
Vader: Nether Imp and Terror sphere sprites
Damien Daurio: Gore Imp sprites (edited by Dusted)
Neoworm: Chaos Soul sprites (edited by TiberiumSoul)
Ben2k9: Cyber Baron sprites
Raven Software: Dark Bishop sprites and sounds (Hexen), Legendary Archon sounds (Hexen 2), Chaos Soul, Desolator, Spec Ops Zombie, Overseer, and Hierophant sounds (Quake 4)
id Software: Legendary Vile sounds (Doom 3)
Freedoom: Dark Bishop death sound
Team Shanghai Alice: Spider Masterspark attack sounds (Touhou)
Ghastly_Dragon: Spec Ops Zombie sprites, Code
Xim: Spec Ops Zombie sprites
Vegeta: Spec Ops Zombie sprites
MagicWazard: Spec Ops Zombie and Salvation sphere sprites
Hacx: Unstability sphere sprites
Eriance: Doom Sphere sprites, Plasma Repeater sprites, Explosive Shotgun sprites, Hierophant sprites, Plasma Repeater code, Hierophant code
Relic Entertainment: Former Admiral sounds (Dawn of War)
Lord Cylarne/Ultimate Apocalypse Team: Legendary Necromancer, Legendary Vile, Pain lord, and Overseer sounds (Dawn of War Ultimate Apocalypse mod)
Lazorinc: Legendary Afrit sprites, various ideas
Pillowblaster: Code for various effects
P.H.O.B.O.S: Leg Salvation Sphere idle sound
Daedalus: Code
Harbinger: Code
Legendary: Code
Titanium: Code


Music for the enemies that have them:
Legendary Phase Imp "Audiomachine - There Will Be Blood"
True Legendary Zombie "Audiomachine - Lost Raiders"
Bloody Flandre "AGENT 0 - Bloody Law"
Legendary Necromancer "Dark Souls II OST - Royal Rat Authority"
Legendary Vile "Dark Souls OST - Manus, Father of the Abyss"
Legendary Afrit "Dark Souls OST - Black Dragon Kalameet"
Legendary Archon of Hell "Dark Souls OST - Ornstein & Smough"
Sacrosanct Overseer "The Dark Side of Phobos - Iron Cathedral"