User blog comment:IamJakuhoRaikoben/Chapter 503: The Last Sight Seen, Review./@comment-5303512-20160926122525/@comment-26389992-20160926150115

You've been arguing for the last month that Natsu transforms into a demon or END... there's no transformation. I still did not see a transformation in this chapter. There will never be a transformation. The "tumor" has now been revealed to be his demonic power. Natsu being revived as an Etherious into a human body... he always an Etherious. But the mass of magic in his chest (his curse power I think?) is what is letting him exert his powers as END (this is how I took it). I always figured Natsu can enter an Etherious form cause he's *wait for it* an Etherious but what you kept debating was never and will never happen.