User blog comment:FairyRaven/Fairy Tail Chapter 465: 400 Years, Review and Commentary/@comment-7405046-20151207135907/@comment-26184007-20151207140420

Of course it is a lie from Mard Geer. Zeref revealed END book was found by chance by Mard Geer who later lied about END being part of tartaros. Of course it kinda doesn't make sense that Natsu would be a guild master of tartaros at a young age.