Satha is an enormous snake that lives in the Halls of Horror, a dungeon beneath the Scarlet Citadel, home of Tsotha-lanti. Satha is white, around 80 feet long and is venomous.
When Conan was trapped inside the Halls of Horror, Satha saved the kings life. One of Tsotha's slaves came down into the dungeon, apparently an old Kushite chief whos brother Conan had killed in his pirate days. The slave was about to cut of Conan's head, when the snake suddenly threw the Kushite into the opposing wall, killing him instantly.
The only persons alive that the reptile is known to fear is Tsotha-lanti and his enemy, Pelias.
Robert E. Howard's The Valley of the Worm, a story occuring in a much more distant past, features another member of the species, and describes them in somewhat more detail. Satha's species are claimed there to be the basis for the legends of Set, Satan and Leviathan.