User blog comment:Derax-Pagani/Chapter 502 Review/@comment-24784846-20160917221849/@comment-2214433-20160919175138

I'm sure it was to buy enough time for Mavis to get as far as possible. She created Zeref to distract Irene, even asked her to leave them alone so that Irene would stop extracting Fairy Heart for a moment. Otherwise, I'd like to think that Irene is clever enough to notice that she is suddenly trying to extract magic from an illusion.