Build a world myth. How long does a person have to be dead before they move into the light, cross the styx? Does some ritual have to be perform? If the ritual is not doen they become undead? What do the god(s) have to say about all these people moving back and forth? How about wills?
Building a myth will keep things in line and you will not have to make special rules and the players will understand the reason for things.
Now somethings I would do. Make the girls some form of demon, the bad guy made some deals with the otherside. Or have them become outcast from their families, because in a world where undead are common do you ever trust someone that comes back from the dead?
Work on a myth for dealing with the dead, the undead, and reason for bring them back.
Building a myth will keep things in line and you will not have to make special rules and the players will understand the reason for things.
Now somethings I would do. Make the girls some form of demon, the bad guy made some deals with the otherside. Or have them become outcast from their families, because in a world where undead are common do you ever trust someone that comes back from the dead?
Work on a myth for dealing with the dead, the undead, and reason for bring them back.