User blog comment:IamJakuhoRaikoben/Chapter 375: Supernatural, Review./@comment-5303512-20140314233709

I was thinking back to the Tenrou Arc, Grimoire Heart said that they acquired all the keys to awaken Zeref, but he was never asleep, but then he says that they summoned Acnologia, but HOW!?! Then I thought what if those keys they collected were what summoned him. I still think that maybe Tartarus demons or E.N.D was responsible for getting Hades to fall to darkness.