Yamaso no Oni

Yamaso no Oni was like a huge wall of glowing vapor, with a suggestion of faces momentarily appearing on the surface of the mist. Mounstrous limbs appeared ramdonly to wipe away its foes. It was first seen in the War of Spirits.

This oni was a conglomeration of tortured souls, bound together by Jigoku's will. The soul of every intelligent being killed by Yamaso was trapped within his mass, never to be released or reincarnated.