Kulan Gath is a fictional characters in the Marvel universe who first appeared in 1972 in issue #14 of the 1st volume of Conan the Barbarian.
Kulan Gath was an incredibly powerful sorcerer, whose power approached the level of the Sorcerer Supreme, Doctor Strange. His power was amplified by human sacrifices and his N'Garai masters. Kulan Gath was able to transform NY city and its population into Hyborian Age analogs, project mystical lasers, summon demonic entities, and manipulate flesh and bone.
During the Hyborian Age he was Stygia's dominant sorcerer. He waged war with his bitter rival the sorceress Vammatar of Hyperborea, but then formed an alliance with her. They married and attempted to free the imprisoned Shuma-Gorath from Mount Crom. Who they then attempted to subjugated, and were overwhelmed by the Old One. Each though the other dead, and both headed back home. Kulan Gath returned to Stygia where he had been displaced by Thoth-Amon. For a while he apprenticed uner him, but was later forced out of Stygia due to his blasphemous sorcery. He would later clash with the sorceress (and mutant) Selene Gallio, and had multiple encounters with the barbarian Conan in various kingdoms of the Hyborian super continent.
He returned to life in late 20th century Earth by possessing the body of a worker who found his necklace. Kulan Gath transformed NY City and its inhabitants into a city of the Hyborian Age, enslaving the Morlocks, X-Men, New Mutants, and Avengers. While Selene and Kulan Gath restarted their old feud, the heroes regained their memories and turned on him. Using the mutant Magik, Doctor Strange reversed time to undo Gath's spell. Later a fisherman found his necklace and was himself possessed. Kulan Gath traveled the world and ended up in South America where he took over an indigenous village. In his attempt to ascend to godhood, he attempted to sacrifice a goddess his agents captured to the N'Garai. The Avengers foiled his plans therefore the N'Garai feasted on him.