Gakusanjin

Gakusanjin is a rock demon whose form is from a mountain and owns the Fuyoheki, that conceals his energy and lets him sleep eternally. However, Naraku steals the Fuyoheki to conceal his heart. He then helps Inuyasha and his gang to find Naraku, giving them a demonic aura crystal: if the aura disappears, the Fuyoheki will be near (The gang promises to return the Fuyoheki in return). He is later he killed by the Gyoja.