Daemonic is a novel written by Stephen Laws. It was first published in 1995.
Description[]
No one has seen Jack Draegerman for 20 years. He lives in a huge fortress known as "The Rock", its interior a crazy structure of labyrinthine, descending corridors, with no way out. But now he has summoned seven apparently unconnected men to visit him, and he's prepared to pay for the privilege.