Banshee is aligned with the cult
When killed, and there are cult alive, they don't officially die but go into sort of idle state (can't see death chat either) - the cult can choose a target for the banshee to possess and take over during the night.
Can only happen once, and if there are no cult alive the banshee just dies. When brought back, they're just converted to a cultist. Role is revealed when they die (so town knows to expect a possible resummon) but the resummon is not revealed.
I recognize that "death is permanent" is a thing, but that's why I specifically say it's a state of idleness and they don't see death chat at all.
This gives cult a potential 1kill possibility. It works like disguiser.
Alternatively the banshee can choose to target someone to possess and their old body dies without the resummoning nonsense.
*shrug* could be cool