Planet of the Damned — Harry Harrison

Brion Brandd has just become the champion of his planet by defeating all the other contestants in “The Twenties.” Many men train all their lives for a chance to be the winner and Brion is ready to savor his victory. But not so fast! When a former winner challenges Brion to do something truly meaningful and heroic with his life, Brion sets off to save the planet Dis from a war that will surely destroy the entire planet. Dis has a hostile environment that nearly kills Brion before he even gets to meet the natives. Then he needs to figure out how the planet and the species that have evolved on it work together so he can solve their political problems.