Aleister Crowley

Once the greatest magician in modern magic history, more than half of all modern magicians are affected by this man's established theories, and two-fifths of them are direct followers of his ways. Having stretched the boundaries of sorcery farther than the advances made in the last few millenia alone and written many top-class spellbooks like, it is no surprise that many mages were outraged when this eccentric genius literally "dumped" all his magic abilities and decided to "ace it" in the field of science, thus establishing the Academy City and becoming its hidden monarch.
 * When he chose to stop using magic and was running for his life from a hoard of enraged stalker magicians, he met the Heaven Canceler, who eventually helped him found Academy City in a far-eastern island of Japan and also provides help in this ex-magician's new goal; to extend his lifespan for as long as possible by having all but his consciousness rely on the power of machines.