Hōraijima

Horai Island was a place where yokai and human lived together in peace, resulting in many Hanyo children. Since Hanyo were unaccepted by the world, a barrier was put up to separate them from those who would shun them. Every fifty years, the barrier would weaken, and Yokai would attack the island. Among them, were the Four War Gods. There was a battle, to stop it Lady Kanade, a priestess from the island, sealed the Four War God's powers into a box, and threw the box into the sacred Cauldron of Resonance. When she did this, her spirit was sealed into the Cauldron as well. The War Gods realized, that if they threw a Hanyo in the Cauldron, they could regain their power, little by little, though they were only able to do this every fifty years, when the barrier weakened. When the Cauldron of Resonance was destroyed, the island collapsed. Now it is nothing but a memory.