User blog comment:Ncduru/War Is Finally Here! Predictions, Theories, Rants & Raves/@comment-7418318-20151008074429

Hmm... you predictions 4 and 5 made me thing of something.

Imagine if Zeref noticed the bond between Lucy and Natsu. Maybe he wants to experiment around a bit with the two of them and see how he can use Lucy to manipulate Natsu.

Alternatively, he might intend to spare Lucy because his brother cares for her. With all the kicks in the balls he got from loving people I think this isn't very likely, but still a possibility, depending on how much of Natsu's current personality would remain once E.N.D. is awakened.

Or it's a loyality test to see if E.N.D. is willing/able to kill Lucy after his awakening.