Fate/Omnitrix

Beau Jones has faced many challenges from the common criminal to superpowered aliens trying to get the Omnitrix, the most powerful device in the universe allowing the user to transform into different aliens including an omnipotent god known as a Celestialsapien, with many figures willing to commit unforgivable sins just to get it. But now at age 17, Beau must face his most dangerous challenge yet, a free-for-all fight to the death with all of the contestants possessing a familiar known as a Servant, spirits of legendary figures from both history and myths where the 'rules' are used as suggestions, all while trying to fight along side a reluctant ally called Rin Tohsaka