I'm just going to post world building updates until I get a full cast, first off, why are there so many vampires in Sunnydale?
I, personally go for a grey approach to storytelling, and hate the idea of evil as a motivation, but how do you explain all the vampires popping up in Buffy, it's like the Sabbat are gearing up to fight the Camarilla, props to anyone who gets that, and then taking the time to bury the recruits. In this world, the number of vampires in good old Sunnydale is instead caused by the fact that the town is built on a Hellmouth, and this one in particular causes there to be a 35% chance of coming back to life as a vampire, no matter how you died, independent of a "family line" like the Order of Aurelius, but naturally subservient to the bloodlines. All members of a direct line can sense each other when near and can tell when one dies regardless of distance. Also, vampires need to feed on a pint of human blood a day, double for animal, or they will begin to weaken, desiccate, and eventually lose higher brain function, until they can no longer move. They cannot die from starvation, though a starving vamp, one who has gone 3 or more days without any blood, or a month without a proper supply, cannot heal like normal. Next, a vampire's body will always eventually return to it's state right before death, and yes, a virgin will always be a virgin, a cripple a cripple, and so on and so forth, unless the healing is altered mystically. My final note on vampires is that there are only three ways to kill them. Wood piercing their heart while it is still in their chest, separating their brain from the rest of their body completely, and anything that burns them.
Next thing up, why crosses, holy water, and biblical exorcisms work, and when.
I have to change cannon here because this doesn't make sense otherwise. God is real, all the gods are real. God with a capital G, cursed a human, Cain, with vampirism. Vampires, in turn, suffer from burns because of Jesus sacrifice on the cross imbuing the symbols of that with something anathema to the demon within them, forgiveness, which magically burns them because they are demons. Holy water is due to the fact that it is holy, and any artifact blessed by a priest of God will cause burns. Finally, demons and exorcisms. This works only if the demon is possessing a living host, and is originally from a truly biblical hell dimension, by that I mean a terrible place that would make Pinhead feel at home.
I hope to be able to start this game up soon. If you have a disagreement with how I decided to make things, please message me personally so that we can discuss it, and I will try to accommodate anyone who wants to play