Core of a dragon? What's that? Since the gryphon hates it, you'd think it's a part of a dragon, but there's no way those humans would be able to beat a dragon when a gryphon is already an unimaginable opponent for them. Perhaps those people of the east are just scavengers that actually sneak in the shadows, waiting for one dragon to finish another dragon, and then they go and steal the fallen dragon's core (whatever that is).