[Kuritza]

Great infantry and terrifying Hydras, lots of mages incapable of good combat spells. No national summons worth mentioning.
With a booster, your mages can cast foul vapors though - that might compliment Hydras. Otherwise,I believe that Serpent Cult's only hope for the late game is a properly designed God. Perhaps a rainbow mage to improvise with whatever available resources. Early on, it may be capable of a good rush; I am curious whether archers are a good counter to Hydras or not.

P.S.
I tried taking drain and playing a wannabe-Mictlan, it didnt pay. Researchers are bad already, drain makes them terrible. It takes a while to build a second castle, and then it will be a very long time till your heretics 'clear' drain from it, if they do at all. Regrettably, they lower dominion, not wipe scales. I think they may be of some use to suppress enemy dominion as you invade somebody, not your own.