It is the dragon from which both of the existing characters changed.
gazoodragon which changed of will unlike graygazoo understands the reason to fight,
and is a dragon with the very strong will which is going to protect a friend.

yukidragon is the dragon from which the gene of the dragon which yuki had from the first solved the seal, and changed.
Regardless of will, it was changing also here by anger or sadness among the beginnings.
But it is fighting now to which the reason to fight was taught for the friend.
It seems that it does not think of strangely itself from whom she herself changes to a dragon.