User blog comment:IamJakuhoRaikoben/Chapter 415: And It Shall Become Your Will To Live, Review./@comment-24546844-20150110204315/@comment-4829046-20150111092106

I think he would have remembered better if it was such a short time ago. And was it said that Weisslogia and Skiadram were killed in X777?

I got the impression that maybe like Atlas Flame and Zirconis, the souls were originally clinging to something else but then found some orphaned children and decided to materialize so as to look after them and maybe raise some humans that can stop the apocalypse. When their souls were deteriorating, they assimilated into the bodies of the DS and could only be seen under certain conditions where the magic was at its peak and maybe nearing 'Dragonification', hence explaining why Faust, Zero and Igneel could see the Dragons.