Spoiler.
It doesn't quite add up that the God King was able to return because Tir Cendalius - or whatever he is called - was weakened by the Elves' Deathfog genocide. Surely the lack of imps / orcs would have provided the opportunity beforehand. Anyway, I always operated under the assumption that orcs/imps were in the game but simply not in the areas you went to. Diversity and a lack of thereof is a thing, right?