Zaō Gongen 蔵王権現

Also Kongō Zaō Bosatsu 金剛蔵王菩薩. The deity of Kinpusen 金峰山 in Nara, one of the most important deities of the Japanese religious mountain practice sangaku shūkyō 山岳宗教. Zaō Gongen typically looks like a tantric deity: blue-black in color, his hair stands on end; he grimaces and shows fangs and he has three eyes. His right hand holds a thunderbolt or vajra *kongōsho 金剛杵 above his head; his right foot is raised while his left hand is at his hip in the sword mudra tōken-in 刀剣印. There are minor variations in his depiction, but he is always characterized by his enormous vitality, his pose that of leaping, or perhaps alighting.
According to legend, the founder of Shugendō 修験道, *En no Gyōja 役行者 practiced on Kinpusen and prayed for a deity who could accomplish the salvation of all sentient beings. First, a deity who looked like *Jizō 地蔵 arose, but was rejected as too mild; then the fierce figure of Zaō Gongen arose, and was accepted as equal to the task. Originally he was believed to be a manifestation of *Shaka 釈迦. He is sometimes identified as a form of Kongō Zaō Bosatsu , who appears in the Kokūzō 虚空蔵 court of the *Taizōkai mandara 胎蔵界曼荼羅 which developed in esoteric teachings in China, but is generally believed to be a Japanese invention.
In the mid-Heian period, when the cult of *Miroku 弥勒 grew popular, Kinpusen came to be known as the inner sanctum of Miroku's paradise, Tosotsu naiin 兜率内院, and Zaō Gongen was considered a manifestation of Miroku. Zaō Gongen was the guardian of Kinpusen (Gold Mountain), which was believed to contain gold treasure that would become accessible when Miroku appeared on earth.
This was a major site of sutra burials, a practice said to have been introduced from China by the monk Ennin 円仁 in the 9th century. Copies of sutras were buried along with the donor's instructions for their future benefits. The sutras were expected to rise and bear witness to the religious devotion of the donor.
The cult of Zaō Gongen was carried throughout Japan along with the practices of mountain religion and there are many images of him, including small metal sculptures buried with sutras. The earliest dated image (1001) is an engraved mirror owned by Sōjiji 総持寺 in Tokyo.