User blog comment:Bato of the Heavy Iron Rock Hammer/God Serena theories/@comment-24784846-20150731212931/@comment-24102956-20150731220438

Makes sense since the common threat in the world is Acnologia if God Serena had defected to Alvarez just to defeat the Black Dragon. Zeref may have a good form of persuasion as he was Emperor Spriggan that convinced God Serena into joining his side despite the dark history of the Black Wizard in Ishgar. And I agree with you if the only reason he defected is because he knew they couldn't beat Alvarez. It's going to be a major disappointment in his character.