Legend of the Tailed Beasts
In the ancient Japan, according to the legend, each elemental god was sealed into an elemental shrine. Out of the 9 Bijuu, 5 of them were elemental gods, those being Shukaku, of the Wind; Kyuubi, of Fire; Isonade, of Water; Raijuu, of Lightning, and Kaku of Earth.
In the Legend of the Tailed Beasts, the 5 elemental gods were sealed with instruments called “The Tools of Power” (法器). Not all of them are known, and their translation may be not accurate, but all resemble a type of varied container (kettle, prison, altar, etc.)
After researching for a while, I’ve discovered that the “Tools of Power” descend from the “Eight Immortals” from the Chinese mythology. They’re deities who transfer their individual energy to each “Tool of Power”, that is able to give life or destroy evil. Together, the eight tools are called "Covert Eight Immortals" (暗八仙); (Though only five appear in the Legend, and it may be a varied version of it). The Immortals are: Immortal Woman He (He Xiangu), Royal Uncle Cao (Cao Guojiu), Iron-crutch Li (Li Tieguai), Lan Caihe, Lü Dongbin, Philosopher Han Xiang (Han Xiang Zi), Elder Zhang Guo and Zhongli Quan.
There were respective shrines dedicated to these elemental Bijuu scattered through Japan’s territory, being the Fire shrine the strongest. Though, the shines keep releasing spiritual energy even while the Bijuu are sealed within sleeping, and this power from the 5 shrines goes to the Five-Tails: Houkou.
After Yamata no Orochi got the legendary sword Kusanagi no Tsurugi from the Kusanagi Clan, it defeated Nekomata and Houkou (Check Yamata no Orochi’s tale).
Yamata no Orochi then proceeded to release a tremendous amount of dark power to awaken the five elemental Bijuu, that were sealed in the 5 shrines, with the purpose of bringing chaos between worlds.
