E.C. Tubb 
Lallia 
The Dumarest Saga Book 6

Dumarest continues his restless wandering — combing the spaceways for an ancient and almost forgotten planet called Earth. Then, on a primitive world, he fights a giant mutant for the life of the lovely psychic Lallia — and wins a vital clue that could lead him to the end of his quest . . . (First published 1971)