The slave of the ring

The slave of the ring is a monster summoned by the wizard Thoth-amon to kill his master and "all with him" in The Phoenix on the Sword. It is described as follows "Its outline was not unlike that of a gigantic baboon, but no such baboon ever walked the earth, not even in Stygia" and "The hideousness of its face transcended mere bestiality. It might have been the face of an ancient, evil mummy, quickened with demoniac life. In those abhorrent features the outlaw's dilated eyes seemed to see, like a shadow in the madness that enveloped him, a faint and terrible resemblance to the slave Thoth-amon."