Yep, Pythium has the Serpent Cult. Extra bonus snaky stuff.
I haven't played with that dominion theme yet so I can't give you too much in the way of specifics, except that the description explains the concept pretty well.
To paraphrase: Pythium couldn't hold back the darkness after Ermor fell, so they recruited aid from the Sauromancers. Even after the lizardmen left, their strange ways have continued to greatly influence Pythium's development and thus was born the Serpent Cult.