Thatguyhsagun wrote:you can do what you wish with daemon armies. Theres fluff aspects (no khorne with tzeench) but theres no official rules as to how many you can have
The true rivalries are;
Khorne vs Slaanesh
Tzeentch vs Nurgle
Khorne may think Tzeentch a weaklin glittle wretch for hiding behind his magic trickery and not slaming a massive axe into everything's face, but Slaanesh represents the carnal lust and greed that is the complete opposit of Khorne's sense of honour & valuing martial prowess above all else.
As for how to combine the Gods/how many to use?
Ironically enough, the outright "safest" thing to do is to build a rivalry army! By taking some Tzeentch & Nurgle units w/Instruments for example, you can all but prevent the Warpstorm table from nuking your units. (only 3 results are actually 'bad' for you at this point)
Going mono-God is cool and fluffy and all, but getting your opposit God's result on the Warpstorm table can be rather painfull... (especially Khorne hating on Slaanesh is you're packing alot of T4 multi-wound units!)