User blog comment:THE TERRIFYING TITANIA/Is there a connection between Master Mavis and Zeref?/@comment-121.7.146.112-20140514121506

My theory is this: Igneel knew about E.N.D and recruited the help of Grandine and Metalica(or something) to help fight it. Knowing they might not survive, he asked Mavis to protect their souls in the form of Lumen Historie, thus you can see Igneel and Grandine conversing in the anime. Mavis thus knew of Zeref this way as Igneel told her about it.