User blog comment:FairyRaven/Fairy Tail Chapter 413: Book of E.N.D., Review and Commentary/@comment-112.204.148.104-20141225061029/@comment-4829046-20141225094721

Then again, it could show that Zeref had developed and can now create way better Demons and thus render the Etherious as older models. Maybe he needs the book to do anything big though since Obra was just a leech.