User blog comment:FairyRaven/Fairy Tail Chapter 391: Gray vs. Silver, Review and Commentary/@comment-7418318-20140705180252/@comment-5598380-20140706011830

At first, i thought that the magic which came from Edolas was the one that made Zeref appear on Tenroujima. I mean, he was probably hiding on Edolas, then when the reverse anima was activated he was returned to Earthland. Just a theory though. XD