Mordiggian is a fictional deity created by Clark Ashton Smith in his Zothique story "The Charnel God". The entity was later incorporated into the Cthulhu Mythos as a Great Old One by Scott D. Aniolowski in his Call of Cthulhu roleplaying game.
Described as swirling darkness, a gigantic shadow, or a worm-shaped column, Mordiggian is worshipped by several human cults and cults of ghouls as a symbol of Death. His name is used in Zothique, Man's last continent, and it is possible that this gigantic creature is the same as Shaurash-Ho or even identical to Cynothoglys. The name may also find its origins in medieval France, being a corruption of the Latin "Mortician" (to do with the dead).
Mordiggian also seems to be the main subject of The Ghoul's Manuscript and Cultes des Goules.