Great Fiend, Yamigedo (character)

"Yamigetou", is an evil monster, and Ikazuchi's buddy.

Anime Biography
Yamigetou is first seen literally eating a planet after it was destroyed by the Hundred Demons, according to the big 8, its the fourth planet they've destroyed. He and Ikazuchi targeted the Earth next. Sometime later, the Hundred Demons and Ikazuchi arrived on Earth and settled on a cave where Ikazuchi drew their power while talking to Yamigetou who was in a spirit like form.