User blog comment:FairyRaven/Fairy Tail Chapter 465: 400 Years, Review and Commentary/@comment-5303512-20151207143157/@comment-5303512-20151207175507

There is still the issue of END creating curses, I doubt Mard Geer could have any connection or tap into the One Magic in order to make curses. Mard Geer didn't know everything about Zeref or Natsu, yet knew quite a bit. There is also the fact that Zeref told Natsu either he or END will kill him. There is even Igneel giving Natsu specific instruction not to open or destroy END's book, it is obvious that there is still a connection between Natsu and the book and there is still more to END.