"...a colossal shadow that was not wrought by anything in the room. It filled the portals from side to side, it towered above the lintel -- and then, swiftly, it became more than a shadow: it was a bulk of darkness, black and opaque, that somehow blinded the eyes with a strange dazzlement. It seemed to suck the flame from the red urns and fill the chamber with a chill of utter death and voidness. Its form was that of a worm-shapen column, huge as a dragon, its further coils still issuing from the gloom of the corridor; but it changed from moment to moment, swirling and spinning as if alive with the vortical energies of dark aeons. Briefly it took the semblance of some demoniac giant with eyeless head and limbless body; and then, leaping and spreading like smoky fire, it swept into the chamber." ("The Charnel God," by Clark Ashton Smith)

Mordiggian is a fictional deity in the Cthulhu Mythos. He is worshipped exclusively by ghouls, although other races may offer up their dead to the Charnel God as appeasement and not as actual worship. The ghoul priests of Mordiggian cover themselves in long, hooded robes of funeral-purple, and silver skull-like masks. A tome known as The Ghoul's Manuscript deals with Mordiggian and its cult.

Although Mordiggian is known mostly within the Dreamlands, it is assumed that the Great Old One may also enter the world of waking men through the same grave-tunnels and tombs that its ghoul followers use. When the Great Old One appears all fire and heat is sucked into its swirling void-like body, instantly lowering the temperature by many degrees, and filling the area with a deathly cold and still air. All within the presence of the Great Ghoul are blinded by the weird changing, dazzling form of the necromantic god.

Mordiggian attacks by engulfing victims, sucking away their life force, and dissolving the body: nothing remains of the Charnel God's prey, and they are never seen again in the waking world or in the Dreamlands. This Great Old One does not appear to be especially malevolent, and has been known to spare those who have not personally offended the god or his followers (ghouls) in some way.