Raijū is a legendary creature

Legendary creature

A legendary creature is a mythological or folkloric creature.-Origin:Some mythical creatures have their origin in traditional mythology and have been believed to be real creatures, for example the dragon, the unicorn, and griffin...

 from Japanese mythology

Japanese mythology

Japanese mythology is a system of beliefs that embraces Shinto and Buddhist traditions as well as agriculturally based folk religion. The Shinto pantheon comprises innumerable kami...

. Its body is composed of either lightning

Lightning

Lightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...

 or fire

Fire

Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....

 and may be in the shape of a cat

Cat

The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...

, tanuki

Tanuki

is the common Japanese name for the Japanese raccoon dog . They have been part of Japanese folklore since ancient times...

, monkey

Monkey

A monkey is a primate, either an Old World monkey or a New World monkey. There are about 260 known living species of monkey. Many are arboreal, although there are species that live primarily on the ground, such as baboons. Monkeys are generally considered to be intelligent. Unlike apes, monkeys...

, or weasel

Weasel

Weasels are mammals forming the genus Mustela of the Mustelidae family. They are small, active predators, long and slender with short legs....

. The form of a white and blue wolf (or even a wolf wrapped in lightning) is also common. It may also fly about as a ball of lightning or fire (in fact, the creature may be an attempt to explain the phenomenon of ball lightning

Ball lightning

Ball lightning is an unexplained atmospheric electrical phenomenon. The term refers to reports of luminous, usually spherical objects which vary from pea-sized to several metres in diameter. It is usually associated with thunderstorms, but lasts considerably longer than the split-second flash of a...

). Its cry sounds like thunder

Thunder

Thunder is the sound made by lightning. Depending on the nature of the lightning and distance of the listener, thunder can range from a sharp, loud crack to a long, low rumble . The sudden increase in pressure and temperature from lightning produces rapid expansion of the air surrounding and within...

.

Raiju is the companion of Raijin

Raijin

is a god of lightning, thunder and storms in the Shinto religion and in Japanese mythology.His name is derived from the Japanese words rai and shin . He is typically depicted as a demon beating drums to create thunder, usually with the symbol tomoe drawn on the drums...

, the Shinto

Shinto

or Shintoism, also kami-no-michi, is the indigenous spirituality of Japan and the Japanese people. It is a set of practices, to be carried out diligently, to establish a connection between present day Japan and its ancient past. Shinto practices were first recorded and codified in the written...

 god

Deity

A deity is a recognized preternatural or supernatural immortal being, who may be thought of as holy, divine, or sacred, held in high regard, and respected by believers....

 of lightning. While the beast is generally calm and harmless, during thunderstorm

Thunderstorm

A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...

s, it becomes agitated and leaps about in trees, fields, and even buildings (trees that have been struck by lightning are said to have been scratched by Raiju's claws).

Another of Raiju's peculiar behaviors is sleeping in human navel

Navel

The navel is a scar on the abdomen caused when the umbilical cord is removed from a newborn baby...

s. This prompts Raiden to shoot lightning arrows at Raiju to wake the creature up, and thus harms the person in whose belly the demon is resting. Superstitious people therefore often sleep on their stomachs during bad weather, but other legends say that Raiju will only hide in the navels of people who sleep outdoors.