User blog comment:Miskos3/Fairy Tail Chapter 506: The Broken Bond, Review/@comment-23887466-20161017143817/@comment-1776824-20161019024414

Although, he is quite literally teetering on the edge of insanity and darkness. Devil Slayer Magic has that effect. It effectively makes you into what you slay, just on a moral level. The Gray we were used to would never do this. Although he was faking it in the Avatar arc, the face Gray made when he said he was going to go after and kill E.N.D. was the Gray we see now.