The Faded Sun: Kutath (1979)

Amazon.com Product Description (ISBN 0879975164, Paperback)

Kutath was an ancient world and a dying one. In ages past, its best sons and daughters had gone to the stars to serve as mercenaries in the wars of aliens. Now the survivors of its star-flung people, the mri, had come back-in the form of a single woman, the last priestess-queen Melein, and a single man, the last warrior Nuin. And one other-the human Sten Duncan who had deserted Earth-s military forces to swear service to the foes of his own species-.