The Ring of Eternity, was a neutral magical item from the episode, "The Tale of the Guardian's Curse.
It is a powerful Egyptian ring, it was in possession of Mina the Guardian. How the ring was created and how it came into her possession is
Mina the Guardian was a powerful Goddess and a Queen of Egypt, over 3000 years ago. It was believed that every spring, Mina would use this ring to bring forth life from the earth.
Also, Mina would use this ring as a weapon, she used it to turn her enemies into stone. Whether or not she had to trick them into wearing it, or wear it herself and point it at them is unknown.
There is a curse to this ring. There are many people who believe that when putting this ring on, they will be granted immortality. However there is a catch. If one is to put this ring on immediately, they will be cursed and turned into a stone statue for eternity.
The being, must first come into contact with Elixir of Life. They must first apply the Elixir to their finger and then put the ring on to avoid the curse.
This ring was found inside the sarcophagus of Mina the Guardian in 1994. The wicked and greedy Dr. Capel-Smith yearned it for himself. He believed it would grant him immortality. However, since he did not apply the Elixir of Life to his finger before putting it on, he was cursed and he transformed into an Egyptian stone statue for eternity.