The Mind Thief by Colbby

After an accident in space, Jay from Earth, crash-lands onto a new world. He is rescued but enslaved and trained to race carts. After many adventures with his driver and now his friend, Taki, he eventually wins his freedom and leaves with his new wife to his adopted land. The Regal of Mordia learns that attacks are taking place in the south of Mordia. It appears that someone is taking control of men's minds and is turning them into naked savages, but how and what for? Jay and Taki are asked to investigate because as the Regal's race champions they have a legitimate excuse to travel to the south where strangers asking question seem to disappear.