I created a custom mummy, and started in West Africa. My vassals are both vampires adhering to the local culture and religion, so it turns out that both of these things combined causes them to rebel immediately. They also have a few other modifiers, such as viewing my religion as EVIL, and hating mummies. Maybe a mummy's vassals should also be made mummies upon creation?

Anyhow, the vassals obviously form an independence faction, and their dynamic is... interesting. See, the whole family line of my western vassal are infernalists. I can imprison their childer with a just cause (known infernalist), but not the head of the house, for some reason. They all have the Infernalist trait, though, so I have no idea if the ruler's proclivities are publicly known.

And if I were to start around the Web of Faith, well, that's largely Setite territory, and there's a mutual hatred there. So that's not a great starting spot either. Not sure how I'm supposed to play this as a mummy.