Heaven's Door. The Doors of Despair, #4

Maya San Lucas had been lost in her dreamworld for the better part of five years. Desparia was just a fantasy world for her to explore during stretches of boredom at school and at home. Going to that world let her have adventures, exploring secret locations, and searching through towns and cities for loot to come away with. The life of a thief was so much more exciting than high school, especially with no friends to speak of.
After escaping the hell of Hell, Maya and her friends had returned to the depths of the emperor's stronghold. Some were emboldened by what they had seen, more determined than ever to see the emperor deposed. But Maya had brought her own demons with her on her return to Desparia. As her demons stalked her, Maya's newfound magic grows stronger, making her more dependent than ever on her friends by her side.
And with more doors behind them than in front of them, the group pushed on to their destination, even as they experience some of their worse losses yet. Jared didn't understand what was happening to him. He was too young to know the power seated deep within him, destroying whole towns around him. But when he meets Celestia and her fae people, he learns that he is a mage, and starts to come to terms with what that meant.
As he sets out on his journey to rid the world of evil, he starts seeing his own magic as part of the problem. One that he was determined to rid the world of. The only problem was, how to do that without hunting down and killing every mage that ever lived.