Board Thread:Warhammer 40k General Discussion/@comment-14745711-20140911102114/@comment-6078851-20140916133443

the gods are not choosy about who feed them: there are hundreds, possibly thousands, of sentient species in the galaxy that feed the realm of chaos. while worshipping chaos helps them feed they don't actually need followers to gain power, simply the emotions of hate, despair, joy, etc etc, in quantity is enough - there is actually very few species that don't contribute to the gods: the likes of necrons or tyranids are a serious minority when it comes to fueling the gods. as du'un points out the gods like humanity only because they are so numerous and easy to feed from.

if humanity ended up extinct then that just leaves room for plenty of other races to expand, and with greater numbers comes a greater volume of emotion and a greater contribution to the realm of chaos, which is why the human race provides such a measurable impact - numbers. but the gods don't need them as there are plenty more species to fill the gap humanity would leave.

one of the theories i've read on this wiki regarding tzeentch's birth is that since he's the god of change, progress, time, mutability, and all that good stuff, he may have existed before warp space was 'broken'. not as a chaos god (obviously since the realm of chaos didn't exist) but more like a primal force, sorta like he is the force that causes evolution and change. then when the warp was broken it provided an arena in which this primal force could coalesce into an entity. an extension of this theory is that the old ones tampering with warp space may have been tzeentch's first scheme - to have caused the old ones to unwittingly break the warp in order for the primal force of tzeentch to form into an entity. i know that this theory is pretty heavy in 'unbelievability' but i really like it.