User blog comment:Miskos3/Fairy Tail 520: Dragon or Demon, Review/@comment-4933386-20170205092919/@comment-7418318-20170208064410

You got some things mixed together here.

The Dragons didn't go into the bodies of their forster children to make them DS, they did it in part to keep on existing after Acnologia basically killed them and in part to produce anti-bodies against the eventual Dragonification.

Having a Dragon or a Dragon Soul inside your body is NOT required to become a Dragon Slayer.