The T’au Empire has annexed the planet of Cao Quo, but its population constantly resist the embrace of the Greater Good, and Artamax, a cunning Space Marine of the Raptors Chapter, has kicked off an armed rebellion. In retaliation, the ethereal Yor’i assembles a council of Fire, Earth, Water and Wind Caste members to fight the insurgency, but the mounting threat is greater than any of them could have imagined.