User blog comment:IamJakuhoRaikoben/Chapter 413: The Book of E.N.D, Review./@comment-83.253.84.32-20141222153307/@comment-9595671-20141223055211

There has to be one, we know Rogue's future was the result of him. It seems like he does want everything to be destroyed, but its like he can't do it yet.

He seemed to target Tenrou Island for a reason at the time, Zeref mentioned it was mainly due to Grimoire Heart.

In fact it seems like whatever his reasons are, they're related to Zeref since he's only shown up when Zeref's presence was strong.