A Tengu Mask. Buddhism long held that the tengu were disruptive demons and harbingers of war. Their image slowly changed over time into one of protective, yet still dangerous, spirits of the mountains and forests.
Tengu (天狗, "heavenly dog") are a class of supernatural creatures found in Japanese folklore, art, theater, and literature. They are one of the best known yōkai (monster-spirits) and are sometimes worshipped as Shinto kami (revered spirits or gods)