A kinsmen of House Lannister.
This is a new character, not drawn from the books, and the details of his exact relationship to the main line of the Lannister family is a matter of speculation. It has been suggested that Alton may play a role similar to Ser Cleos Frey in the novel, as that character has a Lannister mother and in fact fights for the Lannister side in the war.
Introduced as a prisoner to Robb Stark, he is sent to carry Robb’s demands to King’s Landing, and then returns to imprisonment. Placed in a cell with his older cousin Ser Jaime, he speaks to him of his admiration, and then listens as Jaime suggests he has a plan to escape… only to be swiftly and brutally killed by Jaime, who then uses this as a distraction to escape.