Note: Since I had not read the J.M. Lee books yet, and we don't know much of the character herself in the show, I can only provide information from the Dark Crystal Wikipedia, plus the general knowledge made canon thus far. Design and Bio will be altered once ("IFFFFFFFFFFFF") Season 2 is ever given a God Damn go.

UrSan was the Swimmer of the Mystics, and (presumably) a Female. She was also part of a special enclave of Mystics to live exile from the main group, the others been urSen the Monk, urGoh the Wanderer, urLii the Storyteller and urVa the Archer. She was the half of skekSa the Mariner (aka the Captain) and together they were once the UrSkek SaSan. Based on the fact these two have character traits related to water, SaSan may had been an Oceanographer by trait.

After the Division, urSan followed her 15 other bretheren to exile moving to the Valley of the Standing Stones were they took refuge from the Skeksis. In time she develop her own traits and identity, meditating via swimming. At some point, she left the Valley to swim the Bodies of Water of Thra.

Ages later, when the Gelfling learn from Rian the dark truth of the Skeksis nature and began to mount the Resistance, urSan provides help to Naia, Tae, Onica and Amri to escape the grasp of her counterpart skekSa, as well giving them advise. She seem to have a constant role, similar to Lii and Va in the books. Indeed all the Mystic are quite active in the Resistance, as their connection with the Skeksis is known, and the heroes try to capture the Lords of the Crystal to not kill the Mystics and help reborn the UrSkeks. Through the ordeal they provide guidance.

As skekSa haunted the Gelfling that ruin her control over the Sifa, and had her banished by the Skeksis, urSan suffered the wounds the Mariner developed. By the end, urSan helps capture skekSa in a tree, in the Great Sog, with the Sacrifice of Maudra Laesid, the mother of Gurjin and Naia.

Canonically, in the Age of Resistance series, neither urSan and skekSa are seen taking part of the events unfolding, but is easy to surmise the two are alive, as skekSa is mention by name when the Skeksis are thinking of recalling their best fighters back to the castle to fight Rian and the Resistance. However, by the time of Dark Crystal film, urSan is among the deceased 10 Mystic/Skeksis Pairs.