User blog comment:Miskos3/Fairy Tail 528: Dragon of Magic, Review/@comment-25693405-20170330220926/@comment-25111584-20170331115913

A minority (of maybe even one) guesses that it's Ur. Hardly classifiable as "people."

Given that guesses such as Ur, Ultear, Irene, Celestial Spirit Queen, Miss Moon Drip, etc. are clearly not tenable, I'd hardly call them the worst thing possible simply because they are impossible. The worst things possible are things that should not even be considered, but actually have a high likelihood of being true. Anna or Layla, Rita or some other Dreyar female, Dragneel or Acno mom, and, for some inexplicable reason, Cornelia or Mika.

Actually the worst thing possible has already happened. Some female comes out of the blue and suggests a method to defeat Acno. Pretty much a classic example of an asspull; but then that isn't really the topic here, just the parent which everyone has moved past...