User blog comment:IamJakuhoRaikoben/Chapter 297: The Face of the Girl I Saw Back Then, Review./@comment-5192763-20120902090859

I got an idea about the dragons' graveyard thing(a very short idea). My theory is the GMG arena held the Dragon King's festival before and those skeletons are the corpse from the old Dragon King's festival and now every XXX years it will be hold again.

P.S Sorry for bad english.