Planet of Adventure Omnibus

Tschai is a planet orbiting the star Carina 4269, 212 light-years from Earth. It is populated by three alien, mutually hostile species; the displaced, native Pnume; and various human races, some of whom live as slaves or clients of the aliens. Each of the four novels relates Reith's adventures with one of the species, and is named after that species. In order, the books are:
City of the ChaschServants of the WankhThe DirdirThe Pnume