Yamata no Orochi is a giant serpent with eight heads and eight tails, originating in Izumo Province. Recorded in the Kojiki (712 CE) and Nihon Shoki (720 CE), it is described as moss-covered, vast enough to span eight valleys and peaks, with eyes like red winter cherries.
The kami Susanoo slew it to rescue Kushinadahime, and in its severed tail he discovered the legendary sword Kusanagi. That sword passes into tradition as one of the three Imperial Treasures of Japan.