The War Lord — Steven E. Wedel

Tarod, a young man from the mountains, comes into civilization looking for help fighting off the slavers harassing his people. When he learns that the peaceful city of Nevara is holding a tournament to choose a new war lord, he joins the ranks of gladiators in hopes he can win and use his position to influence the king. His youth, inexperience, and the dark machinations of a wizard prove to be more challenging than the battles in the arena.