I've been trying to figure out a good way to get some Chaos Marines working with Daemonkin and here's what I came up with after thinking about it for 10 minutes or so:
CSM:
Kharn
Belakor
2x 10 Cultists
Spartan/ceramite/dirgecaster/Screams of Lugganath legacy of ruin (for 12" dirge)
Daemonkin allies:
D-Thirster
20 Bloodletters
20 Flesh Hounds
also a Void Shield Generator w 3 shields
Would this just absolutely suck in most cases? I think it could be pretty fun, fast and certainly furious if they get anywhere. I think invis and the voids and maybe shrouding if possible would really help things out a bit. Not great for objective games though, just plunging into the lines really.