Tristan de Bois, also known as "The Black Knight" was the older brother of Ygraine and Agravaine de Bois, the brother-in-law of Uther Pendragon, and one of Arthur's maternal uncles. A former friend of Uther, he turned against him after the death of Ygraine. Many years after his death, he became the deceased uncle-in-law of Guinevere, the wife of his nephew, Arthur.