It's been 15 years since the invasion. What's left of humanity cowers in fear. Why? Oh.... No reason. Other than the giant alien mothership hovering endlessly in the sky. You see, when the aliens invaded, they abducted half the population, mutating them into horrible monsters. Then they let them go. 10 years later, they rounded up their creations. The aliens for the monsters to fight eachother for competition. They've turned our cities into arenas. So while they live in fancy societies, humans are forced to dwell in caves. Only a few mutations have kept their sanity. Now it's your turn to fight. One day, the things those horrible aliens created may rise up, and fight for their freedom. But first they have to fight eachother.