Not necessarily any moreso than any of the other cities, but it was just a suggestion based on you saying you use magic.

{ Zeref narrows his eyes at the crystal. He's never seen anything like it before, but the way she describes it... ah. It's that kind of magic. }

I'm afraid I can't help with that. { If anything, he'd just corrupt it faster... and he wouldn't risk using Law on it. That'd probably be overkill, and there's no guarantee it would even work. } What, exactly, is it? What is making it grow darker?