User blog comment:Miskos3/Fairy Tail 520: Dragon or Demon, Review/@comment-4933386-20170205092919/@comment-1776824-20170205163543

@Shin: The seeds are physical objects. Natsu is an Etherious with a human body, and having the seed inside him is what tethers his life to Zeref. The Dragon Seed is also very much real, as that's what we've kinda been dealing with for a little while now, but all that does is turn the user into a dragon. Basically, Natsu destroyed both seeds so that way he wasn't going to become a dragon or a demon (since both seeds were growing, despite the former one supposedly not being able to grow anymore). He severed his life link to Zeref, and with it his technical status as an Etherious, and also removed all possibilities of ever becoming a dragon...again. Also, with no demon seed, he doesn't (supposedly) have access to demon powers, since the seed was transforming him into the demon with the powers in the first place.