User blog comment:Woest/Raven Tail/@comment-4829046-20131119155845/@comment-24066070-20131119165344

I think Zeref wanted Ivan to find more info about LH. He may have reasoned that a former member who is the estranged son of the current master would know how to obtain that info.

About Ivan getting hold of the information and keeping it to himself, somehow I don't see him fooling or blackmailing Zeref.