I am not familiar with that particular creature but it sounds like a custom monster (or at least 3rd party). It has some themes of the Spirit Oni (mask) and the Exiled Shade ('possession'), so it could be a haunted mask of a Spirit Oni that once served as a familiar for a transmutation wizard.
What were the levels of the characters? That might help narrow down the list of monsters you need to search through.
The dungeon was a CR 10-12, I will look into the Oni and I am pretty sure it wasn't 3rd party(I never allow 3rd party, too many bad OP instances with characters) but it might've been since I have had no luck in finding it.
Hello fellow GM's and players, I have run into an issue with my game;
A while back, they entered a Transmutation wizards tower and I found a pretty interesting enemy/monster for them to encounter...a mask that would possess/consume the wearer's soul and just become them albeit with the mask still covering their face.
I for the life of me CANNOT remember what it was called but I vaguely remember those descriptions of it; consuming the wearer, the creature just being the mask, and if the mask was removed from the body it would just fall to the floor.
Anyone have any idea what it is called? It would really help because for whatever reason(without knowing it's true intents)they...recruited it to join on their adventure. Major thanks.
P.S. I have searched in google, the forums, and I have had 0% luck in firguring it out and looking through every single monster entry is just...a lot but I will keep trying.