Lucifer's Ring

"Well, the key to completing my ensemble maybe."

Lucifer to Amenadiel

'Lucifer's ring' is a ring that Lucifer Morningstar brought with him to Earth and always carries with him.

History
Before being in the possession of Lucifer Morningstar, the ring belonged to Lilith, who took it, before being expelled by God, from the Garden of Eden. Originally, its stone was white but after Lilith decided she no longer wanted to be immortal, she transferred her immortality into the stone, turning it black. She later gave it to Lucifer.

This ring, along with the Pentecostal Coin, were the only two things Lucifer brought with him to earth. Lucifer even wears it when he strips down naked.

Amenadiel initially thought that this ring, that Lucifer always wore, was the key to the Flaming Sword since he believed Lucifer to be God's, Favorite Son. Lucifer is knocked unconscious and stranded in the desert. All his possession are stripped from him, save for this ring and his pants.

Trivia

 * Description: A silver/platinum ring with a black rectangular-shaped stone (Onyx).
 * As the ring holds Lillith's immortality, it's reasonable to believe it can be granted to someone else.
 * The ring disappears when Lucifer goes full-devil mode.