Chronodyne

Chronodyne was a material substituted by the Fourth Doctor for the sixth segment of the Key to Time. He used it so he could make use of the Key's power, but only temporarily as it began degrading the chronodyne. (TV: The Armageddon Factor) One source posited that subtle damage from the chronodyne caused Romana I's regeneration. (PROSE: The Lying Old Witch in the Wardrobe)

The Twelfth Doctor utilized chronodyne generators to entrap a Skovox Blitzer. (TV: The Caretaker)