The Clock of the Time Dragon was a large mechanical device, operated by a party of Dwarves, which could supposedly tell one secrets of his or her life, in The Wicked Years.
Many years later, Elphaba consulted the thing, and it revealed her true father: the Wizard of Oz. She refused to believe it, however. (Wicked: The Life and Times of the Wicked Witch of the West)
Nor would later come to join the traveling group operating the Clock of the Time Dragon, but she could never understand it. (A Lion Among Men)