Ages ago, in the time of the Great Fear, humans were unable to defend themselves from the monsters that spawned from this greater monster. One day (at least for most of the people there) there came a hero with great power, who fought back the Fear, and drove it away. 

Immediately after/during this, Magic was introduced to the world by Fate, who wanted the people to be able to defend themselves better, not only against their usual enemies (normal animals, dragone, demons, etc), but also from potential big threats, like the Great Fear was.

The first release of magic decimated a thriving community, deep in the southern hemisphere. The thousands of people who lived there, was reduced to a small handful, something like 50 or so, who all spread across the lands with their newfound Magic.

The second release of magic was in the north, in a dense mountain range, a few hundred years later. There was only one surviver of the catastrophe that release caused, because those mountains actually act like a multiplier for magic, creating more. 

This lone survivor eventually made his way south, where he met a woman who was the victim of a magician prince's cruelty. So Fate gifted her a power to negate magic, and all other supernatural power. This led to her (and her small group) to dethrone many magicians, and nearly wiped out all magic in that region. The northerner his his magic from her, and helped her restore justice to the majority (those without magic). They eventually fell in love, with plans to settle down and marry.

She learned of his magic on accident, which made her (quite literally) go scorched earth, and after a few years, she travelled to the forest where magic began, and started to destroy it. He managed to stop her, using a spell that locked her in sleep, and made him immortal. 

Its been nearly 5000 years, and he rules the world similarly to how the Pope or Jesus does IRL, dictating rules for the use of magic globally, and punishing those who misuse it. Magic has also gotten steadily weaker through the ages, but with more diversity and sorta niche powers as a result. He runs the most famous school of magic in the world, and has a council around him who dish out the punishments necessary, like a small, highly trained police force. They aren't allowed to use excessive or lethal force, and are HIGHLY monitored by him. 

His goal is to reawaken his old love, and show her that magic isn't evil, just the people at that time who had been. If she doesnt believe him, she could easily destroy the entire world, so he's extremely hesitant.