The description from the museum:

Zaō Gongen is the guardian deity of Mount Kinpu in Yoshino south of Nara. Zaō appeared at the behest of En no Gyōja, who prayed for a powerful protector of the mountain. The deity was described as a combined manifestation of the Buddha Shakyamuni, Thousand-Armed Kannon, and Miroku. These three deities were viewed as the past, present, and future protectors of the world. Zaō’s appearance derives from portrayals of fierce Buddhist deities.