Shas'O Kais was a Tau Fire Caste Commander and student of the Tau Commander Puretide who led the Tau military forces that fought on the planets during the First Multiverse War. He was dispatched to quell the troubles on the Tau worlds, which had been attacked by the forces of the Axis of Empires and the Coalition of Independent States. Kais commanded a detachment of the Fire Caste and the Tau's primary xenos allies, the Vespid and Kroot. He was also dispatched with the Ethereal Aun'el Shi'Ores to secure and hold the capital city on Kronus and keep the world within the Tau Empire's fold. Kais was a strong yet merciful commander, often offering his enemies multiple chances to surrender, with their refusal to serve the Greater Good resulting in annihilation.