A bit off topic but Sammaels voice in the game is played by one of the actors from Mad Max 2. He was the 2nd in command biker with the mohawk that went crazy mad after every little thing that happened
Anyway I've always thought that alot of the Darksiders demons would transfer well into Chaos and if I wanted I could do a lot of "counts as" daemons based off of Darksiders enemies so for instance I could represent a Chaos Sorcerer with say wings and the mark of Tzeentch like a Caster from the game (snake bodies, horns, 4 arms and floated) use the Tyranid Ravener tail with some differant bits.
Obliterators could be like the Shadow Legion champions with the huge cannons, Spawn as Minions (the fast hound like ones) that could be a mix of gaunts/ghouls etc.
Noise Marines as the Banshees, Plague Marines as those corpse things that explode when you kill them, a dread could be the Growler or whatever it's called (the chubby demon dragons) or a Trauma, the Jailer would be a good
DP or Greater Daemon but it's too Nurgleish and I don't want to directly represent the gods you know?
But I'm just focusing on the Shadow Legion and Fallen for me Greater and Lesser Daemons for now I may go back and do more later for Apocalypse (take a Mawloc and represent it like the Stygian

).
I had an idea, what if I combined Blood Letters and
WHFB Beastmen to make the lesser daemons with some armor and
GS work? I want the models to be inspired off of Darksiders but they don't have to be exact matches.