Slaves of an Alien Game: Book 1. Slaves of an Alien Game, #1

Caden works at all night diner in a small town near the interstate. When a man comes in late at night, asking for access to the roof, Caden knows the man is a bit off. But his ruffian nature and a small bribe makes Caden decide to let him go up."It's a scavenger hunt, " the man says. Caden thinks he's being helpful when he finds the item, a black orb, but when he touches it, he unknowingly becomes a competitor in an intergalactic competition, that ends in a battle to the death.
Manipulated and lied to, drugged by the alien Incubus, Raghib, whom he is now allied with, he must train his lizard battle creatures to fight for him on an unknown planet with rules he barely understands. He has little chance to survive and although he wants to trust, Raghib, who will earn his freedom if Caden wins the battle, he worries he is simply being used. A bit of truth is revealed when one of the Game Wardens takes a liking to Caden, but his alien species is known to eat humans, so Caden isn't sure if the desire is that of hunger or true romance.
Either way, Caden is nothing but a slave to their alien games.