Wikipedia
Tharizdun
In the World of Greyhawk campaign setting for the Dungeons & Dragons fantasy roleplaying game, Tharizdun is the god of Eternal Darkness, Decay, Entropy, Malign Knowledge, Insanity, and Cold.
He was imprisoned ages ago by a coalition of deities to prevent the destruction of existence itself. Although imprisoned, Tharizdun still has a degree of his original multiverse-threatening power: he is officially a Divine Rank 11 (out of 20) deity, as of Dragon #294. His holy symbols are a dark spiral rune and a two-tiered inverted ziggurat known as an obex. His holy number is 333.