User blog comment:Hitsuji Mamoru/Servant Creation Room 2 : Guess of the Who/@comment-32599925-20170805033316/@comment-32599925-20170806033151

Kariya is the human, yes.

The other one... well, he's somewhat draconic, yes, but it depends on the portrayal. The myths are somewhat inconsistent except they all agree that he's pretty much the worst thing that could happen, and it took a god-sized critical hit to even stun him.

He never got killed, so that's why the relationship between the host human and the spirit in this Servant is inverted.