The Mythril Ring is used to seal the Djinn and remove the curse that was placed on the people of Sasune and Kazus. Originally give to King Sasune by Takka, Refia's adopted father, it was passed on to Princess Sara who took it with her into the Sealed Cave.
When the party meets Sara, she ask to join them and defeat Djiin, but when they fight him, he used the power of the darkness, rendering the Mythril Ring useless. It was only after the party fought him and won that Princess Sara could use the Ring to defeat him, washing it on the sacred spring of Sasune Castle.
mithril" is a metal found in many fantasy worlds. It was originally introduced by the fantasy writings of J. R. R. Tolkien, being present in his Middle-earth. It resembles silver but is stronger than steel, and much lighter in weight than either. The author first wrote of it in The Lord of the Rings, and it is retrospectively mentioned in the third, revised edition of The Hobbit in 1966. In the first 1937 edition, the mail shirt given to Bilbo is described as being made of "silvered steel". The name mithril comes from two words in Sindarin—mith, meaning "grey" or "mist", and ril meaning "glitter".The word "mythril" or "