They paused for a moment by a wooden sculpture of a boy holding a dog. Then a movement caught Joy’s eye. Lord Joven’s reflection in the hall mirror was beckoning to her even though he himself stood motionless. She almost ran in fear, but if she did then she would have to explain herself later, to her husband and maybe also to her guest. The reflection held up a piece of paper and moved it towards her. Pretending to adjust her hair, Joy moved to the mirror and took it.
Once her husband - Lord Villefontaine - had returned, Lady Joy excused herself for a moment and went to her chamber, where she opened the note. It read: “Return to this mirror after nightfall and be sure you are alone.”
Joy was more afraid than ever, but when night fell she could not resist returning. And this time she was not surprised to see Lord Joven’s reflection there without him. How was it possible, she asked, for a man’s reflection to be there without him? He replied that what was a reflection depended on which side of the mirror one was on. Then he held out his hand. She hesitated, so he asked: Do you dance?
Joy stepped through the mirror and they danced.

The mirror secret spread to Urthauld from the far West, early in the age of exploration. It cannot be learned; either one is born with access to it or not. The reason for this is simple: most people’s reflections copy their actions precisely, with never the slightest difference between them. To harness the mirror secret, that symmetry must be broken.
Although the most common route to possession of this secret is to inherit it, there are masters who can manipulate the reflections of others in such a way as to bestow the potential for the secret upon them.
As for what can be accomplished with mirrors, the range of feats is almost as numerous as the practitioners themselves. The root of all of it is the ability to separate one’s reflection from one’s own position. From there it can be sent to explore or spy on others unseen. Next comes an affinity with one’s own reflection enabling a sharing of emotions or even thoughts. In an environment with many mirrors this is almost like being in two places at one time.
More difficult to learn is the art of passing through mirrors into the mirror realm. Once mastered, this technique can be used to hide and can smuggle the secret wielder into otherwise inaccessible buildings. It is possible to create pairs of mirrors each of which shows the reflection from the other.
There are places in the world where the mirror world itself differs entirely. Whole buildings stand there which would be invisible without the aid of a mirror and an innocent traveller might pass right through one, aware of only a faint unease as their reflection was forced to take a more difficult route.