User blog comment:IamJakuhoRaikoben/Chapter 449: Mavis & Zeref, Review./@comment-99.65.101.58-20150825082127/@comment-7418318-20150825083031

That monster was about to kill all those innocents, so it wasn't for the sake of a single person.

Sure some might have escaped, but if Mavis hadn't cast the spell most of them would have died anyway.