In a moment of crisis for the T'au Empire, the enigmatic ethereal Yor'i assembles an elite Elemental Council – a veteran Fireblade, a water caste spy, a peerless air caste pilot, and a maverick earth caste engineer – in the hope of curtailing the growing insurgency on the planet Cao Quo. But as a full-scale planetary insurrection looms, enemies more cunning than Yor'i's council could have imagined begin to surface from both sides, and Cao Quo soon finds itself teetering on the brink of being plunged back into a dark age of ignorance, and all-out war.