User blog comment:IamJakuhoRaikoben/Chapter 415: And It Shall Become Your Will To Live, Review./@comment-25111584-20150110183754/@comment-9595671-20150110192020

Its possible that Grandeeney was using Milky Way as a way to prolong their lives.

But we still barely now anything about Dragons' abilites as a whole yet so I dunno