User blog comment:FairyRaven/Fairy Tail Chapter 407: All for My Demise, Review and Commentary/@comment-7418318-20141101194846

I have an alternate theory to E.N.D. = Natsu.

Maybe Natsu is only a recent creation of Zeref's. Maybe he met Igneel by chance and he stuck a bargain with the Dragon so that Igneel would raise his creation in a way that he would be able to kill Zeref, but wouldn't be a hazard (or not too much of one anyway :P ) to mankind afterwards.