Cauldron of Resonance

The was a powerful barrier device used to project a time barrier around the island of Hōraijima. The lyrics to the "Song of the Spirit Sending" were carved on the cauldron's gate in an ancient writing. The cauldron gates would open when the left hand of a yōkai and the right hand of a human simultaneously pulled the two release mechanisms on both sides of it.

History
Many yōkai invaded Hōraijima when it appeared in the outside world due to the time barrier weakening then, especially to hide it from Kirinmaru and Zero. The Shitōshin were among the invading yōkai. Priestess Kanade was able seal up the Shitōshin's true power inside a jewelled comb box and placed it inside the cauldron at the cost of her life. The cauldron was later corrupted by the Shitōshin and used to sustain their power by sacrificing a hanyō inside it every 50 years.

During the story
When it was Asagi's turn to be sacrificed, Inuyasha intervened in order to destroy the cauldron. Instead, he and Asagi were pulled into it. Everyone else attempted to open it to save them. The were able to partially open the gate after they read some inscriptions on the cauldron. It was damaged when Inuyasha used his Kongōsōha to escape from the inside with Asagi. It was later completely destroyed by his brother Sesshōmaru with his Sōryūha during the latter's battle with Kyōra. Because the Cauldron was a vital part of the island, after it was destroyed by Sesshōmaru, the island later vanished following the conclusion of Inuyasha's battle with the Four War Gods.

Legacy
Since the island's Cauldron has been destroyed and Kirinmaru has awakened by his elder sister Zero, the hanyōs will go to a new secret village led by Shiori as she puts up a barrier from yōkai to invade the village until the solar eclipse when she loses her power because a Moth yōkai Gaga Gozen comes to devour half demon children, in which Miroku must protect the village until it ends.

Message
A message was written on the cauldron to provide a clue on how to open the gates.

English= Unless you have permission to be here; leave at once. This place belongs to me alone. Only those who possess love and tenderness shall be allowed to place their hands on it. Nihongo= ここにいる許可がない限り、 すぐに出発します. この場所は私だけのものです. 愛と優しさを持っている人だけがそれに手を置くことが許されます. Rōmaji= Koko ni iru kyoka ga nai kagiri, sugu ni shuppatsu shimasu. Kono basho wa watashi dake no monodesu. Ai to yasashi-sa o motte iru hito dake ga sore ni te o oku koto ga yurusa remasu.