Heart of Arhriman
The Heart of Arhriman was an enchanted stone belonging to the sorcerer Toth-Amon, who kept it in his lair, the Crystal Palace after stealing it from a group of rival wizards. The Heart was possessed of different magical properties. None but the one mentioned in the Scrolls of Skelos could touch it with her bare hands. Others would crystallize and then vanish if they touched it. Toth-Amon also used the Heart as a crystal ball of sorts, to spy on his enemies.
After Conan defeated Toth-Amon, Jehnna, the chosen one, was able to procure the Heart and place it into a bag which Bombaata carried. When the group arrived at the lair of the Keepers of the Horn, Jehnna used the jewel for its true purpose: to open the mouth of the stone dragon inside which the Horn of Dagoth lay.