[one-shot]
As Celestia goes over her records of time and recounts several friends she used to have, along with her supposed immortality and the aging of objects around her she begins to feel saddenned. While she remains young and beautiful in the eyes of the populace for all eternity, she can't help but feel the need to know of her fate, and that of her sister. While there ARE two creatures that could tell her, she knows more than anypony not to disturb them. So, instead, she decides to summon one of the knights of the apocalypse, Death.
Death is, as many might imagine, universally hated for taking away loved ones, but also loved for helping reunite with said loved ones and keeping balance with the populace. He is the only one who can help tell Celestia of her future, of Twilight's future, of Luna's future, and the future of the world as a whole. What will the ever silent being reveal to her when he only reveals these facts to the dead. As everyone knows, dead folks tell no tales.
(I'm not sure if I should qualify the Grim Reaper as an "other" or an "original character")