Santa Claus is a Fable that lives on the North Pole, each year he delivers presents to the good and coal to the bad. He is revealed to be a Paladin of the Hope for Justice or the Hope for Reward.
He pens down the list of naughty and nice children from all over the world and rewards them accordingly on Christmas Eve. Instead of travelling the world visiting one house at a time he has a version of Omnipresence in which he visits all the houses simultaneously in a single trip.
If someone happens to come across Santa during his delivery, they have the option to ask Santa a question with the cost of receiving no present from him that year, but getting an answer to their question instead.
Santa Claus appears sparingly across the story of the Fabletown citizens. He caught Jack trying to steal his list. Another time he conjured the dead wife of Flycatcher for one last kiss to turn him back into a man. The Wolf children also interact with Santa on a few occasions.
Finally, in his role as one of Hope's Paladins, he helped Rose Red decide which kind of hope she would champion.
Despite being one of Hope's paladins, he directly answers to Winter Wolf as its shown when she asks for his obidience in siding with her mother