Photo by Bibi Saint-Pol
These beings are immortal with everything that implies, they are the bound ghosts who watch over the holdings & treasures of the cults of the Medusa. Medusa cult's wizards or necromancers use ancient rites from Mu to lock these souls inside their stone prisons. These tormented & insane souls are continually dragged back & forth between reality & the cold none existence of the Outer Darkness. Their souls begin to take on the numbing non existence of the void. While they have all of the normal attacks of a ghost ala the Astonishing Swordsmen & Sorcerers of Hyperborea's Referee's Guide. These poor insane souls also gain an additional ability to leave deep burn like rivulet cuts in their victims in the physical world marking their victims as afflicted by the 'Deep Curse'. Those so marked are literally the damned walking the world. The 'deep curse' is a horrid thing. Those that survive such an attack will be subject to a 'fear' spell effect & animals of two hit dice or less will flee from them. Family members & others will sense unconsciously the mark of damnation on the victim. They will shun them & turn on them within 1d4 months. The deep curse is a lingering curse of damnation that follows any survivors of these mad things across their lives and beyond. It also marks the soul after death as prey for the ghost to feast upon. After the victim's death their souls will be dragged deep into the Outer Darkness where their tormentors await them. Rival cults of Tsathoggua worshipers may know legendary practitioners of the dark arts able to remove the Deep Curse.
Only a witch bound to Tsathoggua of fifth level or better will know the dread rites & secrets for removing the curse. This will involve a major magic item of no less then five thousand gold pieces or better for the curse to be removed. Some cults of Medusa worshipers use these dread guardians to extract ransoms from highly placed royalty & Hyperborean officials. Often this is done to cause chaos & pure malice something that the medusa revel & excel at.