I can remember a book, possibly a short story, where the protagonist is a knight who is sent on a quest to help a noble lady deal with a tyrannical uncle.
The key mechanic of the plot was that the lady's family had the magic of swapping their spirit with another creature using collars with a spell stitched into them. The knight is introduced to this and the knight and the lady swap places with hunting hounds that the lady's family breed.
Some other things I can remember are that the hounds' spirits inhabit their owners' bodies while they are swapped and there is an incident where they are attacked and the hound/humans try to fight by biting their assailants and that the uncle is using the same magic with a bear.
The setting was possibly Arthurian, magic was unusual. The rough outline of the plot that I can remember is that the Knight is pried away from a feast accepting a quest to help a Lady that nobody else was interested in doing, possibly because of the feast and/or the impoverished nature of her domain. The Knight and the Lady travel to the Lady's kingdom with the Knight intending to return for the next feast in a year with the tales of his exploits. There is a romantic sub-plot between the Knight and Lady. They reach the kingdom, confront the Uncle and some sort of conflict. The Uncle controlling the bear was taboo and somehow risky for him, possibly because of the strong experience of being a bear. The bear was chained and its ribs broken, so it was sort of safer as it was kept as a dancing bear by the Lady's family, but unleashed by the Uncle to further his ambitions.
I read this around 20 years ago, but the book is probably older. It would likely have been a YA novel, or some sort of collection.