Q'yth-az was first used by Chaosium for its Call of Cthulhu RPG in 1994.
Q'yth-Az is a Great Old One that lives on Mthura a lightless world. It's a stationary entity that extends and absorbs frost-like tentacles. Anything living that is touched by the crystalline tendrils is transformed into formations of solid minerals. By generating large clusters of sharp, heavy minerals and crystals it crushes victims.
It is able to project its thoughts and influences acorss the cosmos via mineral formations. Humans that are psychically sensitive whom come into contact with crystal formations can pick up its projected thoughts, its influence often manifesting in dreams.