The Tythonian War Droids are a number of ancient battle droids programmed to patrol the ruins of Kaleth on the Jedi homeworld of Tython.
"The ruins of Kaleth are overrun with various squads of ancient - and hostile - war droids. A deadly remnant of Tython's mysterious past, the original purpose of the droids has been lost in the mists of time. Some speculate they were once guardians, programmed to protect the powerful secrets of Tython's original Jedi inhabitants. Others beleive the droids were used for combat training by the order shortly after the creation of the first proto-lightsaber. A more sinister theory suggests the droids were somehow involved in the destruction of Kaleth itself. Whatever the explanation, one fact is not in dispute: The droids will attack any living creature that dares to enter the territory they still fiercly patrol."