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

Hmmm.

Timeline 1: Eclipse plan never has Phase II. But doesn't work properly and the two-way gate leads to a massive Dragon Invasion.

Timeline 2: Eclipse plan never has Phase II. Lucy comes back and stops opening of gates. One year later, Gray kills Frosch. Rogue goes rogue and is somehow able to become powerful, escape from Acnologia as well as devise a plan to stop Acnologia's rampage.

Timeline 3: Same as Timeline 2, just a bit more damage during GMG arc. And now Natsu knows about Acnologia's future rampage thanks to Rogue. And we know that they'll win because of this info as this is the main timeline in the series (and they have no Eclipse Gate to redo things if they lose in the end).

So Timeline 2 Rogue is able to give info about Acnologia's rampage because of Timeline 2 Gray's actions. And it's obvious that, with only Lucy's interference, it'd've been Timeline 2 all over again. So something that Timeline 2 Rogue did in Timeline 3 will allow Acnologia to be defeated. So ... well, played, Timeline 2 Gray? XD

All falls apart if Timeline 2 Gray's (or Timeline 2 Rogue's) actions caused Timeline 2 Acnologia to go berserk instead of him just doing it for the heck of it. .-.

Just an observation, not defending Gray. :P