@dee I'm going to wait a bit to disclose further information,  see if we can get one more person before I start spewing details.

@Necromancy Of course, that would be up to the players, but I would rather that the players were free to choose how they interacted with the spirits. This is actually a very important detail that will be addressed when we write up character sheets, as the Manifestation I spoke of in the OP is one of the biggest interactions with a spirit one can have.