User blog comment:Jopjopjop/Volume 18 Spoilers/@comment-16281343-20140622051520/@comment-16281343-20140622060110

Pretty sure the Evil Dragon inside it would Yamata no Orochi. I would be disappointed if he wasn't.

I mean, two descriptions point to him. Multiple dragon heads (self-explanatory, I guess?) were created and it has a poison (YnO's other hame is Venom Blood Dragon).