Xexanoth is a fictional deity created by Clark Ashton Smith in his story The Chains of Aforgomon. Little is known about Xexanoth. He is the enemy of the time god Aforgomon, and like Aforgomon has some control over time. To contact Xexanoth one must defile an altar of Aforgomon, spill one's own blood on the altar and pronounce some of the time god's sacred litanies backwards. Xexanoth can rip certain hours of time from their rightful place and make them happen again. Not only the caster relives the hour however, the entire universe is disrupted by that hour. This will certainly draw the wrath of the time god.
Xexanoth has also been called the "Lurking Chaos" which may point to his being an avatar of Nyarlathotep.