Mordiggian was created by Clark Ashton Smith in "The Charnel God" (1934), set in the city of Zul-Bha-Sair within his Zothique cycle. The entity manifests as a vast, formless darkness and holds dominion over all the dead within the city, which the law requires to be surrendered to its temple.
Its priests wear purple robes and golden masks, and any who attempt to steal a body or desecrate the temple are consumed by Mordiggian directly.