Tytos Lannister was Lord of Casterly Rock and Warden of the West during the period of relative peace from 245 AC to 270 AC. He was known for not being particularly interested in ruling, instead finding the arts and the sciences more interesting. Despite this he didn't want to give up his title because of the massive profits and the enormous societal status it held.
His son, Tymon Lannister managed most of the Westerlands' daily business when his father couldn't. He was sometimes called the "real" Lord of Casterly Rock, since he was a good-natured and fierce negotiator, to the distress of his father.
He died in the year 270, in the middle of the conflict known as Durran's Defiance. After he had stayed behind as his sons went to fight in the Reach, Lord Ronnel Tarbeck invited him for a feast at his hall. Tytos came, but to his surprise was detained and his guards were killed. When Perceon Lannister came to free his grandfather after the fighting was done, Lord Ronnel cut off Tytos' head and threw it at the besiegers. In what would become known as Ronnel's Regret, Perceon's men pummelled the walls with catapults for three days and nights, until the castle was just a blasted ruin.