User blog comment:CNBA3/My Big Three Theories!/@comment-62.234.10.30-20150419010623

Zeref is literally the symbol of taking life away... not giving it. And Mavis seems to have been the closest with Zeref out of anyone. Maybe Mavis is actually Natsu's mother... and gave birth to him before she turned into [SPOILER FOR SOME?] Lumen Histoire.