Mansion of Janus 2 – Ritual and experiment chamber.
Slab
The House is a great unknown. How far does it reach? Who lives there now? Is it nefarious? Does the Architecture make any sense? These are all questions for you to decide. Among the many rooms and corridors we find the research hall there is no way for the uninitiated to comprehend what purpose it serves or what goes on there. But those in the know can figure out the reason and possibilities within.
Comes in two variants: To ritual chamber and the experiment chamber. Both have the option of attaching adjoining rooms behind the hidden door/window. The add-ons come in the basic corpse storage variant and the more nefarious necromancers store room.
As per usual the red square on walls/roof indicate a hidden passage. Remove before play.

That pentagram is delightfully inventive!