Stars Without Number
The insectile Zadak were relatively peaceful trade partners with humanity until the Scream wiped out their caste of psionicallyactive mediators. The remaining Zadak blamed the humans, and after savaging the surface of Polychrome they retreated to their homeworld with tens of thousands of human prisoners. Once there, the humans were put to work helping to maintain the elaborate engineered paradise-jungles of Chot Zadak under the guidance of the ruling Harmony Lords. The humans are kept at medieval levels of technology while their Zadak masters employ sophisticated xenotech to alter certain among them to serve more specific purposes. These modifications usually result in drastically shortened life spans, but a Changed can be faster, stronger, and more perceptive than any ordinary human. The Changed generally serve as overseers and inquisitors of their own kind, watching for signs of rebellion.
A minor slave uprising recently allowed a promising experiment to escape to Polychrome, in a hijacked Zadak ship, along with its Zadak pilot and a human from off world. The off worlder had worked for the Zadak briefly, before balking at the mods they intended to bestow upon him.