The Dragon Masters

Man has warred for centuries with the reptilian race called "Basics". The winner of each bloody encounter has made slaves of the loser—but in this far-future conflict each side improves its slaves with genetic engineering. On Aerlith, men have bred Basics into fearsome troops; on Coralyne, Basics have developed grotesque mutant human warriors. The mysterious Sacerdotes watch and wait for Aerlith and Coralyne's final contest.
Hugo Award winner, 1963.

Cover art by Todd Tennant