User blog comment:Miskos3/Fairy Tail Chapter 486: The Fourth Guest, Review/@comment-4507125-20160524082154/@comment-24734624-20160603235122

I don't believe Zeref had a hand in Acnologia becoming a Dragon either. But what about one of his parents being an Etherious, with everyone but Zeref oblivious to this fact? It'd make sense and it'd be a killer plot twist.

The unholy offspring of a human and a Demon from the Books of Zeref who bathed in the blood of Dragons and became something worse then all three.