Here is my monster for the contest. Guess I'll throw in the full description for him. Bear it with me. lol >.<

The Betrayer: Imprisoned

One of the most powerful supernatural being which some may refer to as "god" or "the ancient one." He's also the last one remaining of his kind, because after he felt the thirst for power, he slaughter everyone, cut open their skull and absorbed all their power and knowledge. His tyranny was put to an end by the Creator himself. Stripped him from most of his power by striking a mystical crystal through his heart, and chained his arms and legs with an ancient spell. He was then banished to wander for eternity in his prison, waiting for unfortunate souls to come by.

Habitat: Ancient prison in the shape of an Aztec pyramid

Attack: - Imprisoned form: When a hero first encounter the betrayer, he can't attack on his own due to the spell bounding him. The floating eye which also act as his sight, however, can summons lightnings and blasts powerful beams to destroy the intruder.  
        - Unchained form: As his health get lower during battle, the sealed which imprisoned him will be broken, and he can use his hand to take out the crystal out of his chest to use as a sword, dealing an outrageous amount of damage.

Note: He floats around. lol