The device is cursed, however. Martha warded her prize possession against others befitting from it. She wove ego-enticing spells into its crystalline structure to slowly turn anyone into a megalomaniacal fiend, delving into a nothing but self-aggrandizing schemes once the curse truly takes hold. Using it, there’s a chance that the seer will witness their own fate or end, running the risk of having their spirit summoned to that point in time to account for a life not yet lived. Unless a very potent mage indeed, the hapless magic user may not be able to return from such a journey.
It's Unwise To Confront a Wizard in the Seat of His Power