Mythril Ring

Mythril Ring, also known as Mythril Bangle, is a recurring piece of equipment from the series.

Final Fantasy III
The Mythril Ring cannot be equipped, but 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. After the party bests him in battle Princess Sara can use the Ring to defeat him, washing it on the sacred spring of Sasune Castle.

Final Fantasy X
Mythril Ring is an armor for Yuna, obtainable if the dominant abilities on any armor are any one Defense +% and Magic Defense +% ability.

The Japanese name of Mythril Bangle is Mythril Ring, and is an armor for Lulu, obtained in the same manner as the English Mythril Ring.