Satha is a Great Old One in the expanded Cthulhu Mythos. Which was first mentioned in two stories by Robert E. Howard; The Scarlet Citadel (1933) and the Valley of the Worm (1934). It's first appearance in Marvel was in issue #30 of the 1st volume of the Savage Sword of Conan.
During the Hyborian Age it dwelled in the southern jungles of the Country of the Worm, terrorizing the Picts. When a tribe of Aesir migrated to the area, he killed them all except for their leader Noird who hunted it down and appeared to slay it.
Sometime before or after, the Old One lived in Koth where it encountered the powerful sorcerer Tsotha-Lanti to whom it submitted. Conan of Cimmeria would end up in the sorcerer's citadel and encountered it two times, both times surviving though not because of his own actions.