Life-timer
From Jenny Everywhere Wiki
Life-timers were magical hourglasses used by Discworld's Death. Every living being had one, with their name inscribed upon it, with Death knowing that their time had come when the sand in the glass ran out. The Jenny Everywhere of that world had a Life-timer, but used her shifting to add more sand to it whenever it ran out, making her functionally immortal (much to Death's frustration). (PROSE: Pratfall)
