Darkness in the Flame by John A. Karr
Heroic fantasy tale, Darkness in the Flame, has a vein or two of Robert E. Howard and Karl Edward Wagner. Mars once teemed with life and death long before Earth did. Rhone is a mixed-blood war slave, the offspring of a sorcerer and half-demon. Shunned by his fellow slaves, he sees little reason to co-exist with them and fight the battles of his masters. In fact, he sees little reason not to launch a suicidal attack on them.