User blog comment:B214/Chapter 498: Gray vs. Invel/@comment-5303512-20160822105845/@comment-1359322-20160822110418

If Invel wants Gray to kill E.N.D. he should just told him that Natsu is E.N.D. when Natsu broke free. Gray may very well snap the very moment he finds out Natsu is E.N.D.