I think Zeref wants fairy heart because it is the key to bringing END out of Natsu. Prior arcs detail that it takes a strong source of magic to bring END out and I think the Etherious in fairy heart is just that. I think Zeref wanted END to come out naturally in Natsu but once he found out about...
First of all this is my first post so be gentle lol.
Second of all I am still not conviced that madara is who he say he is. I think he was defeated by the first but I have several theories to put out there about him.
What if madara is actually his brother? Please correct me if I'm wrong...
