User blog comment:IamJakuhoRaikoben/Chapter 411: Quid Pro Quo, Review./@comment-4489126-20141201153419/@comment-7418318-20141201155213

Someone already said at some point that E.N.D. is a Flame Demon, so Natsu being out won't be a problem if he's going to fight it.

END will open with a fire attack, Natsu will eat it and *bam* back in fighting condition.