User blog comment:IamJakuhoRaikoben/Chapter 477: Transport, Review./@comment-24228963-20160316104252/@comment-4829046-20160316115716

I've always been more inclined towards the

"Obra infiltrated Raven Tail without Ivan knowing about him being anything other than a regular member of his guild and as part of his spying Obra somehow uncovered Lumen Histoire's existence."

Though, I like to think that Zeref already knew where Fairy Heart was. We've seen that he can use some form of teleportation, so if he wanted to, he could just get it anytime. He can be invisible to regular eyes if he so chooses after all. The defensive seals are nothing to him. What he really wants to do is crush those that are defending it and maybe even have his own forces wiped out so that whatever spell he wants to power with FH can be done more smoothly. Or it's just the contradiction curse kicking in with its own reasoning. Maybe it is so that he can clearly destroy Mavis' ideology the slow and hard way.