The story follows a T'au Empire expedition sent to the Imperial-held Yuxa system to investigate the reappearance of a long-lost Water Caste ambassador.
The T'au's idealistic "Greater Good" is contrasted against the Genestealers' biological imperative, which also masquerades as "Unity" and "the Greatest Good".
It explores the concept that in the 41st millennium, there are no "good" factions, only varying degrees of evil.
T'au Empire (specifically the Water Caste and Fire Caste), Gue'vesa (human auxiliaries), and Genestealer Cults . 2. Narrative Summary
The phrase "the greater of two evils" is also frequently used in fan discussions regarding the or Imperial vs. T'au debates. Fans often argue whether the Imperium's brutal authoritarianism is a "lesser evil" compared to the total annihilation offered by Chaos.
Voyle, a former Imperial Navy Breacher who was abandoned by the Imperium and eventually rescued by the T'au. He now serves as a Gue'vesa auxiliary, though he remains haunted by past trauma and voices in his head.