Appearance and Character Edit
Willem is either a blond boy with long hair, and a low peach fuzzy beard that covers his cheeks and jaw, or one with brown hair.
A Game of Thrones Edit
Since his mother Genna is a Lannister, Tion fights with his cousin, Jaime, at the Battle of the Whispering Wood. When Robb Stark wins the battle, he takes Tion as a captive along with the Kingslayer to Riverrun.
A Clash of Kings Edit
King Robb Stark offers to release Tion and his cousin Willem Lannister in exchange for Sansa and Arya Stark. But Tyrion declines his offer, and suggests Lord Medger Cerwyn and Ser Donel Locke in exchange for Tion, and Harrion Karstark with Ser Wylis Manderly for Willem. Tyrion uses these negotiations as a cover to sneak his men into Riverrun and help Jamie escape the dungeons, however the negotiations doesn't work as well as his plan, and Tion remains captive at Riverrun with his cousins.
A Storm of Swords Edit
Blinded by vengeance for two of his sons; Lord Rickard Karstark uses ten of his men to attack both Tion and his cousin Willem while still in their cells. Their killers, along with Lord Rickard, are condemned to death and executed by Robb Stark.