The final monster is an underpowered Mimic (yup, the shapechanging chest aberration) that was created when the cultists kept making sacrifices with an incomplete copy of the Mordenkainen's Magnificent Mansion spell! They found the pages torn out of a book near the cliffs of Ravenloft and mistook the spell for something nefarious "It's complicated! It's arcane! It must be eeeevil!". It became the centerpiece for their hackneyed ceremonies and the framework for a haunted house that keeps rebuilding itself.
The mimic appears as a dollhouse replica of Death House and requires a sacrifice of a silver spoon, a miniature portal carved from ivory and a small piece of polished marble. It also likes to eat the hand, arm and face of the person who feeds it
The mimic appears as a dollhouse replica of Death House and requires a sacrifice of a silver spoon, a miniature portal carved from ivory and a small piece of polished marble. It also likes to eat the hand, arm and face of the person who feeds it
