Coyote Diamond
Coyote Diamond - The world's largest diamond, which Fox sent Jackal and Hyena to steal.
History
Xanatos bought it before they could steal it, saying it would go nicely with the Star of Arabia. Xanatos' purchase of the Coyote Diamond prompted Jackal and Hyena to attempt to steal it from him, and leading to their attempted assassination of him at Xanadu. (In fact, Fox really sent Jackal and Hyena after the Coyote Diamond as part of Xanatos's scheme to recruit Derek Maza to his cause). ("Her Brother's Keeper")