User blog comment:IamJakuhoRaikoben/Chapter 477: Transport, Review./@comment-24228963-20160316104252/@comment-7418318-20160316114014

Obra being one or being associated with one of the shield is a theory that has been around since we saw that shot with the silhoutettes of them.

But with the total lack of information since then, there was no reason to discuss it further, so that's why the topic isn't talked about much.

I got the impression that the majority of us thinks that Obra (whether it is Spriggan related or not) through Ivan was the source from which Zeref and by extension his underlings learned of Fairy Heart's existence.

Some theories go that Ivan was allied with Alvarez. Some theories see Obra as a kind of mercenary who was payed in information rather than currency, or maybe Ivan traded for other favours. Some theories are that 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.