
Originally Posted by
SuperHappyTime
There wasn't really a "Chaos Undivided".
Most of Chaos forces are aligned to one of the gods, or unaligned (as opposed to a "one nation, under chaos").
Beastmen did what they did because they were animals, born humanoid because of Chaos.
Archaeon served himself. He wanted to destroy the Empire by his own means and it was something the other gods were united behind. Don't suck the world into a black hole, and after Archaeon wins the gods probably raise their own champions to kill him too.