The tengu in art appears in a variety of shapes. It usually falls somewhere in between a large, monstrous bird and a wholly anthropomorphized being, often with a red face or an unusually large or long nose. Early depictions of tengu show them as kite-like beings who can take a human-like form, often retaining avian wings, heads, or beaks. The tengu's long nose seems to have been conceived in the 14th century, likely as a humanization of the original bird's bill. This feature allies them with the Sarutahiko Ōkami, who is described in the 720 CE text the Nihon Shoki with a similar nose measuring seven hand-spans in length. In village festivals, the two figures are often portrayed with identical red phallic-nosed mask designs.
Some of the earliest representations of tengu appear in Japanese picture scrolls, such as the Tenguzōshi Emaki (天狗草子絵巻), painted c. 1296, which parodies high-ranking priests by endowing them the hawk-like beaks of tengu demons.
Tengu is often pictured as taking the shape of some sort of priest. Beginning in the 13th century, tengu came to be associated in particular with yamabushi, the mountain ascetics who practice Shugendō. The association soon found its way into Japanese art, where tengu are most frequently depicted in the yamabushi's unique costume, which includes a distinctive headwear called the tokin and a pompom sash (結袈裟, yuigesa). Due to their priestly aesthetic, they are often shown wielding the khakkhara, a distinct staff used by Buddhist monks, called a shakujō in Japanese.
Tengu is commonly depicted holding a magical feather fan (羽団扇, hauchiwa). In folk tales, these fans sometimes can grow or shrink a person's nose, but usually, they have attributed the power to stir up great winds. Various other strange accessories may be associated with tengu, such as a type of tall, one-toothed geta sandal often called tengu-geta.
The term tengu and the characters used to write it are borrowed from the name of a fierce demon from Chinese folklore called tiāngǒu though this still has to be confirmed. Chinese literature assigns this creature a variety of descriptions, but most often it is a fierce and anthropophagous canine monster that resembles a shooting star or comet. It makes a noise like thunder and brings war wherever it falls. One account from the Shù Yì Jì (述異記, "A Collection of Bizarre Stories"), written in 1791, describes a dog-like tiāngǒu with a sharp beak and an upright posture, but usually tiāngǒu bear little resemblance to their Japanese counterparts.
The 23rd chapter of the Nihon Shoki, written in 720, is generally held to contain the first recorded mention of tengu in Japan. In this account a large shooting star appears and is identified by a Buddhist priest as a "heavenly dog", and much like the tiāngǒu of China, the star precedes a military uprising. Although the Chinese characters for tengu are used in the text, accompanying phonetic furigana characters give the reading as amatsukitsune (heavenly fox). M. W. de Visser speculated that the early Japanese meaning for the characters used to write Tengu may represent a conglomeration of two Chinese spirits: the tiāngǒu and the fox spirits called huli jing before the nuances of meaning were expanded to include local Japanese kami, therefore the true Tengu in appearance
The Konjaku Monogatarishū, a collection of stories published in the late Heian period, contains some of the earliest tales of tengu, already characterized as they would be for centuries to come. These tengu are the troublesome opponents of Buddhism, who mislead the pious with false images of the Buddha, carry off monks and drop them in remote places, possess women in an attempt to seduce holy men, rob temples, and endow those who worship them with unholy power. They often disguise themselves as priests or nuns, but their true form seems to be that of a kite.
Throughout the 12th and 13th centuries, accounts continued of tengu attempting to cause trouble in the world. They were now established as the ghosts of angry, vain, or heretical priests who had fallen on the "tengu-realm" (天狗道, tengudō). They began to possess people, especially women and girls, and speak through their mouths (kitsunetsuki). Still the enemies of Buddhism, the demons also turned their attention to the royal family. The Kojidan tells of an Empress who was possessed, and the Ōkagami reports that Emperor Sanjō was made blind by a tengu, the ghost of a priest who resented the throne.
One notorious tengu from the 12th century was himself the ghost of an emperor. The Hōgen Monogatari tells the story of Emperor Sutoku, who was forced by his father to abandon the throne. When he later raised the Hōgen Rebellion to take back the country from Emperor Go-Shirakawa, he was defeated and exiled to Sanuki Province in Shikoku. According to legend he died in torment, having sworn to haunt the nation of Japan as a great demon, and thus became a fearsome tengu with long nails and eyes like a kite's.
In stories from the 13th century, tengu began to abduct young boys as well as the priests they had always targeted. The boys were often returned, while the priests would be found tied to the tops of trees or other high places. All of the tengu's victims, however, would come back in a state near death or madness, sometimes after having been tricked into eating animal dung.
The tengu of this period were often conceived of as the ghosts of the arrogant, and as a result, the creatures have become strongly associated with vanity and pride. Today the Japanese expression tengu ni naru ("becoming a tengu") is still used to describe a conceited person.
In the Genpei Jōsuiki, written in the late Kamakura period, a god appears to Go-Shirakawa and gives a detailed account of tengu ghosts. He says that they fall onto the tengu road because, as Buddhists, they cannot go to Hell, yet as people with bad principles, they also cannot go to Heaven. He describes the appearance of different types of tengu: the ghosts of priests, nuns, ordinary men, and ordinary women, all of whom in life possessed excessive pride. The god introduces the notion that not all tengu are equal; knowledgeable men become daitengu (大天狗, greater tengu), but ignorant ones become kotengu (小天狗, small tengu).
The philosopher Hayashi Razan lists the greatest of these daitengu as Sōjōbō of Kurama, Tarōbō of Atago, and Jirōbō of Hira. The demons of Kurama and Atago are among the most famous tengu.
Creatures that do not fit the classic bird or yamabushi image are sometimes called tengu. For example, tengu in the guise of wood-spirits may be called guhin (occasionally written kuhin) (狗賓, dog guests), but this word can also refer to tengu with canine mouths or other features. The people of Kōchi Prefecture on Shikoku believe in a creature called shibaten or shibatengu (シバテン, 芝天狗, lawn tengu), but this is a small childlike being who loves sumō wrestling and sometimes dwells in the water, and is generally considered one of the many kinds of kappa. Another water-dwelling tengu is the kawatengu (川天狗, river tengu) of the Greater Tokyo Area. This creature is rarely seen, but it is believed to create strange fireballs and be a nuisance to fishermen.
In the 18th and 19th centuries, tengu came to be feared as the vigilant protectors of certain forests. In the 1764 collection of strange stories Sanshu Kidan (三州奇談), a tale tells of a man who wanders into a deep valley while gathering leaves, only to be faced with a sudden and ferocious hailstorm. A group of peasants later tell him that he was in the valley where the guhin live, and anyone who takes a single leaf from that place will surely die. In the Sōzan Chomon Kishū (想山著聞奇集), written in 1849, the author describes the customs of the wood-cutters of Mino Province, who used a sort of rice cake called kuhin-mochi to placate the tengu, who would otherwise perpetrate all sorts of mischief. In other provinces a special kind of fish called okoze was offered to the tengu by woodsmen and hunters, in exchange for a successful day's work. The people of Ishikawa Prefecture have until recently believed that the tengu loathe mackerel, and have used this fish as a charm against kidnappings and hauntings by the mischievous spirits.
Tengu are worshipped as beneficial kami (gods or revered spirits) in various Japanese religious cults. For example, the tengu Saburō of Izuna is worshipped on that mountain and various others as Izuna Gongen (飯綱権現, "incarnation of Izuna"), one of the primary deities in the Izuna Shugen cult, which also has ties to fox sorcery and the Dakini of Tantric Buddhism. Izuna Gongen is depicted as a beaked, winged figure with snakes wrapped around his limbs, surrounded by a halo of flame, riding on the back of a fox and brandishing a sword. Worshippers of tengu on other sacred mountains have adopted similar images for their deities, such as Sanjakubō (三尺坊) or Akiba Gongen (秋葉権現) of Akiba and Dōryō Gongen (道了権現) of Saijō-ji Temple in Odawara.
Tengu appear frequently in the orally transmitted tales collected by Japanese folklorists. As these stories are often humorous, they tend to portray tengu as ridiculous creatures who are easily tricked or confused by humans. Some common folk tales in which tengu appear include: 2b1af7f3a8