The [[Tau]] society is divided into several castes. The Shas, or [[Fire Caste]] composes the Tau's military. The Fio, or [[Earth Caste]], composes the Tau's agricultural, manufacturing and engineering caste. The Kor, or [[Air Caste]], is charged with the Tau's piloting and comunications. The Por, or [[Water Caste]], are the Tau's diplomats, ambassadors and traders. Finally, the Aun, or [[Ethereals]], comprise the Tau's leadership and spiritual guidance caste.