User blog comment:FairyRaven/Fairy Tail Chapter 427: Pitched Underground Battle, Review and Commentary/@comment-31.132.65.54-20150408015850

I think that we might soon learn what happen to Grimoire Heart and where Zeref is hidding. I once made a theory that after Acnologia nuked Tenrou Island, Zeref assumed Natsu died and thought no one will be able to kill, so he decided on an alternative solution. He arrived at Fiore capital and told the royal family about the Eclipse and how to build it. Arcadios original plan to kill Zeref in the past was Zeref wish. I found is strange that Arcadios still called him "Lord Zeref" even right before the Eclipse Gate was opened.

Zeref could have taken Rusty and Kain with him, to teach them. Rusty could be even among the organizers of the GMG, the city from Hidden and the castle from Pandemonium could be his creations. I know this is unlikely, as villains in Fairy Tail don't receive power ups but it would be a nice twist.

Grimoire Heart was mentioned by Avatar, Bluenote appeared, Ultear is still alive somewhere, the Mr Cursey doll was shown with someone name Abel (Kain and Abel?), Briar looks like she got the idea for a haircut from Rusty (ok, this was kinda random). I have a feeling that Grimoire Heart might be just around the corner and that Zeref is involved, eight years is a lot of time to rebuild a guild.

It may be a good opportunity for Azuma and Ultear to come back to the story. Zeref might want them on his side and will remove the side effects and limitations of their magic. I hated what happened to Ultear after the GMG and Gray now !@#$ all over her sacrifice, he don't deserve it, hope Ultear will be back to all her glory :D