Yamata no Orochi

Yamata no Orochi (八岐の大蛇 lit. "8-branched giant snake") or Orochi translated as "Eight-Forked Serpent" in english, is a river beast from ancient japanese folklore.

Mythology
Yamata no Orochi legends are originally recorded in two ancient texts about Japanese mythology and history. The ca. 680 CE Kojiki transcribes this dragon name as 八岐遠呂智 and ca. 720 CE Nihongi writes it as 八岐大蛇. In both versions of the Orochi myth, Susanoo or Susa-no-Ō is expelled from Heaven for tricking his sister Amaterasu the sun-goddess.

After expulsion from Heaven, Susanoo encounters two "Earthly Deities" (國神) near the head of the Hi River (簸川) in Izumo Province. They are weeping because they were forced to give the Orochi one of their daughters every year for seven years, and now they must sacrifice their eighth, Kushi-inada-hime (櫛名田比売 "comb/wondrous rice-field princess", who Susanoo transforms into a kushi 櫛 "comb" for safekeeping). The Kojiki tells the following version.


 * So, having been expelled, [His-Swift-impetuous-Male-Augustness] descended to a place [called] Tori-kami at the head-waters of the River Hi in the Land of Idzumo. At this time some chopsticks came floating down the stream. So His-Swift-Impetuous-Male-Augustness, thinking that there must be people at the head-waters of the river, went up it in quest of them, when he came upon an old man and an old woman, --two of them,--who had a young girl between them, and were weeping. Then he deigned to ask: "Who are ye?" So the old man replied, saying: "I am an Earthly Deity, child of the Deity Great-Mountain-Possessor. I am called by the name of Foot-Stroking-Elder, my wife is called by the name of Hand-Stroking Elder, and my daughter is called by the name of Wondrous-Inada-Princess." Again he asked: What is the cause of your crying?" [The old man answered] saying: "I had originally eight young girls as daughters. But the eight-forked serpent of Koshi has come every year and devoured [one], and it is now its time to come, wherefore we weep." Then he asked him: "What is its form like?" [The old man] answered, saying: "Its eyes are like akahagachi, it has one body with eight heads and eight tails. Moreover on its body grows moss, and also chamaecyparis and cryptomerias. Its length extends over eight valleys and eight hills, and if one look at its belly, it is all constantly bloody and inflamed." (What is called here akakagachi is the modern hohodzuki [winter-cherry]) Then His-Swift-Impetuous-Male-Augustness said to the old man: "If this be thy daughter, wilt thou offer her to me?" He replied, saying: "With reverence, but I know not thine august name." Then he replied, saying: "I am elder brother to the Heaven-Shining-Great-August-Deity. So I have now descended from Heaven." Then the Deities Foot-Stroker-Elder and Hand-Stroking-Elder said: "If that be so, with reverence will we offer [her to thee]." So His-Swift-Impetuous-Male-Augustness, at once taking and changing the young girl into a multitudinous and close-toothed comb which he stuck into his august hair-bunch, said to the Deities Foot-Stroking-Elder and Hand-Stroking-Elder: "Do you distill some eight-fold refined liquor. Also make a fence round about, in that fence make eight gates, at each gate tie [together] eight platforms, on each platform put a liquor-vat, and into each vat pour the eight-fold refined liquor, and wait."


 * So as they waited after having thus prepared everything in accordance with his bidding, the eight-forked serpent came truly as [the old man] had said, and immediately dipped a head into each vat, and drank the liquor. Thereupon it was intoxicated with drinking, and all [the heads] lay down and slept. Then His-Swift-Impetuous-Male-Augustness drew the ten-grasp sabre, that was augustly girded on him, and cut the serpent in pieces, so that the River Hi flowed on changed into a river of blood. So when he cut the middle tail, the edge of his august sword broke. Then, thinking it strange, he thrust into and split [the flesh] with the point of his august sword and looked, and there was a great sword [within]. So he took this great sword, and, thinking it a strange thing, he respectfully informed the Heaven-Shining-Great-August-Deity. This is the Herb-Quelling Great Sword. (tr. Chamberlain 1919:71-3)

Compare the Nihongi description of the Yamata no Orochi (tr. Aston 1896:1:52-53). "It had an eight-forked head and an eight-forked tail; its eyes were red, like the winter-cherry; and on its back firs and cypresses were growing. As it crawled it extended over a space of eight hills and eight valleys." These botanical names used to describe this Orochi are akahagachi or hoozuki ("winter cherry or Japanese lantern, Physalis alkekengi"), hikage ("club moss, Lycopodiopsida), hinoki ("Japanese cypress, Chamaecyparis obtusa), and sugi ("Japanese cedar, Cryptomeria").

This legendary sword Kusanagi-no-Tsurugi, along with the Yata no Kagami mirror and Yasakani no Magatama jewel or orb, are the three sacred Imperial Regalia of Japan

In Shaman King
In Shaman King is the Legend of Yamata no Orochi likened to the Maki River by Asakura Yohmei. He explains to Umemiya Ryunosuke how people once saw the river as a snake spirit who's will decided if their crops would flourish or not, but after the river killed Inada, the princess of the plantation they began to see the snake spirit as a threat.

Trivia

 * It is a common misconception that the "Yamata no Orochi" is a second spirit that Ryu possesses