User blog comment:BlackWizardZeref/Theories on "God Slaying" Magic/@comment-82.20.156.238-20131101071659/@comment-82.20.156.238-20131101160843

Yeah, I was thinking Mavis was a deity which would explain her immense magic/power and the reason why she appears the way she does. Also, being a deity, she doesn't have to be a physical being (she can possess one or go into one if she wanted) and thus sticks to her spirit form.

And, maybe the reason for her relationship with Zeref (letting him jam on her island and shit) is because she was there when it all happened and understands his pain and stuff. Also, maybe Mavis likes staying in the human world because the God world just became too boring for her and she wanted to see what it felt like being human. As a God(dess), she may have even been the Goddess of Fairies or something along those lines.

And maybe, Zeref wants to destroy the human world to save it because he has seen the problems he has caused and this is his method of rectifying his mistakes.