Magic God

A Majin (魔神) is a Magic side term used to refer to a being who can bend all things in the world without exception through magic, something that transcends normal magic and steps into the realm of God, a Magic God.

According to Silvia, the power of a Majin is even more troublesome than a great number of grimoires. With such an interesting prospect, many magic organizations, seek and fear the Majin.

Currently the title is held by One-Eyed Othinus, who stole the title from Ollerus.

Principles
Being a Majin is akin to being the purest, most perfect existence that encompasses every possibility. However, because of this, since it is every possibility, the Majin has a equal chance at succeeding as he is to fail, making everything relating to the Majin's magic a 50/50 shot. This comes from the principle of the Omnipotence Paradox, which asks if an omnipotent being can do anything, can he deny himself; i.e. could an omnipotent being create a rock it can't lift?

Candidates
However, Index can still display some of the potential of a Majin's power when her John's Pen mode is activated, here, she shows tremendous power and can apparently use any spell from the grimoires, although her full potential have yet to be seen due to John's Pen Mode's restrictive thought process, and appears only in certain conditions, such as when John's Pen Mode's remote control is used.
 * Index - is the first character mentioned of being capable of being a Majin, with her having the 103,000 grimoires and is apparently immune to their poisonous nature. However, out of fear of having Index rebel and becoming a Majin, the Church has made provisions to disable her from using any spell by cutting off her mana.


 * Ollerus - is the person that was supposed to have been closest in becoming a Majin that comes only once in 10,000 years but had let it slip through his fingers, when trying to save a kitten. Ollerus wields incredible power enough for him to be wanted by the entire magic side, and crushed all of his pursuers easily.


 * Othinus is the one who later attained the legendary title of Majin from Ollerus, which Ollerus proclaims to have been stolen from him, making her one of the most powerful beings in the Toaru Majutsu no Index storyline.