Yamata-no-Orochi (ヤマタノオロチ, 八岐の大蛇) is a famous monster from Japanese mythology. Specifically, an Asian dragon, which, unlike other depictions of Chinese or Japanese dragons portrayed as good, is depicted as evil and dangerous.
It was a Japanese dragon with eight heads and eight tails, with eyes as red as blood, and whose breath was poisonous. According to the Kojiki and the Nihon shoki, on his body, which spanned eight valleys and eight mountains, grew moss, cedar and cypress trees and on his belly flowed rivers of blood between his glowing flesh.
He was a native of Koshi province (now Hokuriku region) and lived near the Hi River in Izumo. He used to feed on a young girl once a year.
At the end of a battle on Mount Sentsū, he was killed by Susanoo who had provided the snake with eight tubs of refined sake eight times. Weakened by this drink, he could not resist Susanoo's Totsuka-no-tsurugi attacks. Susanoo then found the sword Ama no murakumo no tsurugi (天叢雲剣, lit. "Sword that gathers the heavenly clouds") in the tail of the monster that he had failed to slice, which he later gave to his sister Amaterasu.
One possible interpretation of the legend is that Yamata-no-Orochi actually symbolizes the valley and its floods or perhaps brigands or rival tribes. It is known that the ancient Japanese often demonized their defeated enemies, such as Tsuchigumo, Aterui nicknamed Akuro-ō, the king of the Evil Way, as well as the story of the oni and Momotarō (who would actually represent an ancient kinglet and his subjects subjugated by Kibitsuhiko-no-mikoto).
Thus, the maidens devoured by the snake could have been human sacrifices to appease the cruelty of an Ara-Mitama (荒御霊), or conversely, tribes to buy peace from human enemies, Ame-no-Murakumo then being a metaphor for an excellent sword, with mystical properties, made from the iron sand of the river, domesticated by humans.
The power of this sword, both mystical and martial, was such that it enabled Susanoo to "disperse the clouds gathered in the sky" when he drew it, i.e. to overthrow all opposition or, on the contrary, to unify and consolidate his own kingdom.
In view of its nature and its place in Asian culture, Yamato-no-Orochi has appeared several times in popular culture: