User blog comment:Uraharattack/Ultear Return Debate Area/@comment-31.132.65.50-20160222202806

Many theories comes to my mind. Jellal and Meredy could have healed her, or Ultear herself could have overcome the side effects of her Time Magic and mastered her magic. She said herself that only parts of the Arc of Time exists in this world. It even can be a similar artifact to the Devil Heart that gave Hades longevity and magic power, only it would implanted inside of her.

The theory I'm in favor is that Ultear was brought back because of Ankhseram interference. I always thought it was not fair that Zeref for trying to return the dead to life and meddling with the time continuum was turned into an immortal, but Ultear did all of the above with her Last Ages and became an old lady. Maybe Ultear was treated differently. She gained mastery over time magic and a new life, but in return became some sort of a time keeper that exists outside of the flow of time. Ultear's job now is to prosecute scrubs like Dimaria and Zeref who can't take a warning/advice and keep on playing with powers that can crash the universe.

I think this is the most diplomatic way to go. It won't undermine Ultear goodbye to Jellal and Meredy, because she is not part of their world anymore. And Ultear can still be around for most of the story, since she will need to ensure that the Zeref issue is resolved. Also there is still that Shadow-thing from Future Rogue timeline that ties in with the forthcoming Acnologia apocalypse.