Crystal ball

A crystal ball was an object which focussed psychic powers, often providing a means by which someone could remotely view events which would occur in the past, present or future.

A fortune teller who told Tegan Jovanka's future used a crystal ball. (DW: Snakedance)

Three Carrionites, Lilith, Bloodtide, and Doomfinger, used a crystal ball to view and influence events remotely. (DW: The Shakespeare Code)