When the Demon Queen Echidna launches her invasion of the human realm, the people turn to the hero Leo Demonheart for help. Leo, endowed with insurmountable might, easily repels Echidna's army, saving the planet. Instead of thanks or admiration, Leo is received with contempt and ridicule from his fellow humans, who fear his immense power and believe it would lead to humanity's demise. Banished from the realm he once called home, Leo wanders aimlessly throughout the land until he hears of Echidna's efforts to rebuild her army one day. He returns to the demon queen's castle and offers Echidna his assistance, hoping that demonkind will welcome him as an ally. Naturally, Echidna rejects him right away. However, not all hope is gone.