Hmmm, I was thinking a multi-tribal group of desert nomads for a nation. Or a single person trying to raise an army of the dead and eventually he succeeds.
Well, since you said occult rituals and shit exist, how about a faction/cult that slowly grows and at certain points commit ritualistic suicides to please a god of death/afterlife, also allowing them to have some undead involved. #Deathcult3000
For something like this to work you'll need to have rules limiting the deities so that they can't stay on the mortalplane for long stretches of time, otherwise they could take over an empire, also iI'm in on this idea.