User blog comment:FairyRaven/Fairy Tail Chapter 426: Black Heart, Review and Commentary/@comment-25111584-20150401185614/@comment-25111584-20150402044600

@HL: Yeah, funny that Gray being a douche is one of the reasons Timeline 3 can be saved. XD But, as emphasized earlier, only if Timeline 2 Gray's actions (direct or indirect) didn't cause Timeline 2 Acnologia to go berserk. Actually, we don't have any info on Zeref. For all we know, he might have been the one to instigate Acnologia's rampage as part of his plan to obliterate humans. End boss is still undecided, I'd say. Zeref might prefer acting from the shadows, so F. Rogue might not have known anything about his involvement.

@anon: True, Rogue can never go back if an Eclipse plan independent of his interference doesn't exist. But the Eclipse Plan was begun 7 years before F. Rogue's advent. Only Phase II was F. Rogue's idea. So I don't think there's any paradox there. ;)