What would the embodiment of Time be in Ars Magica? Mechanically it could be of any Realm. What could its embodiment be? Any story can be a faerie, an a demon can claim to be anything, but Time, in various mythologies is the thing that comes before the Magical powers of creation, which come before the Gods of faerie, which come before the current dominance of the Dominion. So Time might be from another Realm completely, something primordial before magic.
If time has a living embodiment is it the Divine, or a demon, or is it some thing that comes from before the divergence of Faerie from Magical? Something that is like the Faerie gods but does not depend, as they do, on human worship? In the short story that follows Time punishes a human for attempting to do what Time does. Is this punishment merely a Magical act? What happens if this creature comes into conflict with the covenant, or, both worse or better they become allied?
You may remember from Ancient Magic that age draws sites are closer to the Magical Realm, so they have higher auras. Can this creature affect this process? Can this creature, as the embodiment of ageing things so that they get close to the Magical Realm, slip places seamlessly into and out of Twilight?
Once Time as he prowled the world, his hair grey not with weakness but with dust of the ruin of cities, came to a furniture shop and entered the Antique department. And there he saw a man darkening the wood of a chair with dye and beating it with chains and making imitation wormholes in it.
And when Time saw another doing his work he stood by him awhile and looked on critically.
And at last he said: “That is not how I work,” and he turned the man’s hair white and bent his back and put some furrows in his little cunning face; then turned and strode away, for a mighty city that was weary and sick and too long had troubled the fields was sore in need of him.
Games From Folktales 