User blog comment:IamJakuhoRaikoben/Chapter 433 & 434: Ikusatsunagi & Demolition Fist, Review./@comment-63.152.122.15-20150511182921/@comment-7418318-20150511204115

He made a contract or something with Ikusatsunagi. He sacrificed his own face so that he could later summon the god.

ANd as HominiLupus said, the sacrifice of the Avatar members' souls was to attract Zeref. That had nothing to do with the god.