The Tale of the Heike describes, 'It's a human but not a human, a bird but not a bird, a dog but not a dog, and it has human arms and legs, a dog's head and a pair of wings, and it flies'; moreover, in the Kamakura period Tendai monks flaunting miraculous efficacy made it an objective to prove the transcendence of Buddhism, and some books, including "Zegaibo Emaki," mention stories that Tengu challenged a Tendai monk to a fight and was defeated miserably.
『平家物語』では、「人にて人ならず、鳥にて鳥ならず、犬にて犬ならず、足手は人、かしらは犬、左右に羽根はえ、飛び歩くもの」とあり、鎌倉時代になると、験力を誇示する天台僧らに、仏教の超越性を証明する為の標的とされ、『是害坊絵巻』を始めとする書物に、天台の僧に戦いを挑み、無残に敗退する天狗の物語が伝えられるようになる。