Leviathan (リバイアサン) is a great yokai that was created around the beginning of the earth. It's yoki was so strong that few could live in it's presence. It dominated the oceans for many centuries until it reached the Sea of Japan. There, it did battle with the great yokai kingdom that resided in the sea. As a last resort, the king sealed his youngest son in sword form, connecting to a seal on the Leviathan itself. In order to maintain the seal, the process must be repeated once every century.
- Immense yoki: This creature had tremendous yoki, even to the point where Shokujin referred to it as the greatest yokai in existance. It was said to be so powerful that it could kill beings with just it's presence if the weren't strong enough with their own yoki.