Im tinkering with a priest type whose perfected a ritual in the last 20 years tired of the harm he sees demons or the possessed inflict (im making him like morty but with diabolism).
The intent is to cleanse a demonic force and it worked sorta (basically a very very  watered down version of the dark hallow). he summons a bunch of them and doesnt try to destroy but convert their energy. It makes him crazy powerfull but also crazy he loses his faith and our heroes have there work cut out for him.

i doubt il be able to make it work but, you know how it is to make an enemy even the munchkin in the group wont want to tangle with.
cant decide if he'll have an ecto suit to make him spawn like or if he'll summon minions and roast our heroes beside the marshmellows