The Onyx Stone

This black gemstone fits in the palm of one’s hand. It is acquired from defeating the commander of the Lost Souls, The Dark Soul. This stone is embedded in a ring located on his finger.

While in the possession of the wielder, the stone can be used to project destructive energy but at the risk of harming oneself. This was demonstrated by Arthur Strathmore during the battle at the Gates of She'Ol.