The lord of Anielle is indirectly mentioned in Throne of Glass, and is directly mentioned in Heir of Fire and Tower of Dawn. He makes a physical appearance in Crown Of Midnight that shows his eldest son, Chaol, making a deal with him that if he stands by him in proposing to the King of Adarlan that Celaena go to Wendlyn then he'll come back to Anielle and rule. This ultimately never happens.
He had spent most of his life defending the villagers from the cruel, mountain tribes of the White Fang Mountains. This changed after the conquest of the local free-folk, bringing peace to the people of Anielle. Lord Westfall could finally focus on developing their welfare.
His son, Chaol, left the title of his heir, to become the captain of Rifthold's palace guard and stay near to his best friend, Prince Dorian. In the process, Chaol's younger brother, Terrin had become heir to the throne.