User blog comment:Sky-Dragoon-Twilight/Weisslogia and Skiadrum, Alive or Dead?/@comment-18654001-20141208200051/@comment-1595565-20141211030437

I think it was some kind of spell like Milky Way, but a step above. If not that then some kind of spirit manifestation spell. I know Igneel inexplicably appeared from Natsu's chest, but we didn't see anything happen to Sting and Rogue like that. I mean, Sting and Rogue killed their dragons themselves, upon the dragons' orders. They were also on their deathbeds at the time. I can understand Mashima trying to mess with us, but I can't understand Weisslogia and Skiadrum messing with them. Also, and this is just my personal take, it would seem that the dragons' light and shadow forms are already somewhat ethereal, so they could very well be ghosts in that regard.