Meidō Stone

is a stone that the Inu no Taishō gave to his lover before his death. He said it would help Sesshōmaru one day but also cause him great danger. It is never revealed where, how or when the Inu no Taishō obtained it but seeing as how it was the last item that she got from her mate and it helps her son in maturing the Meidō Zangetsuha further Sesshōmaru's mother seems to really treasure it as she always keeps it with her.

Powers and Abilities

 * Windows: The Meidō Stone can allow the user to view what events are going on in hell.
 * Portals: The Meidō Stone can open and close portals to Hell. Using this ability can allow the wielder to summon demons from Hell to do their bidding.
 * Resurrection: Like the Tenseiga, the Meidō Stone can bring the soul of a dead person back from the Underworld.

Trivia

 * Although the Meidō Stone has only been shown once in the InuYasha series it's never stated if it has any other type of powers aside from resurrecting and opening portals.
 * It is also unclear if that is the only Meidō Stone in existence or if there are any others.
 * It has at least been theorized in the fanfiction universe for a Meidō Stone (or a shard of it) to grant someone immortality.

冥道石 Meidoseki Viên đá Minh Đạo