User blog comment:IamJakuhoRaikoben/Chapter 497: The Winter Mage, Review./@comment-24951162-20160810202218/@comment-7418318-20160811131746

So Mard "only" lied about E.N.D. being the guild master and founder of Tartaros?

Even if that were the only thing, this is one of the most important things he ever talked about. It's the reason why Tartaros even existed and he lied about THAT. How can you still consider him a trustworthy source of information after him lying about that?

Besides it is not the only thing that Mard lied about. We know for a fact that Natsu never ever was with Mard Geer and thus can't be the one to create curses. So that's at least two things definitively proofen to be lies.

And while there is no absolute proof against it, I am also very sure that the thing with E.N.D. being awakened if the continents magic is wiped out was either an outright lie to give the other Demons additional motivation to do it or just a theory he had which would probably have turned out as reliable as Hades' attempt to awaken Zeref of the cult's attempt to revive Zeref.