Lord Walder Frey from A Storm of Swords is a nobleman whose daughter was to marry Robb. But, when Robb impulsively marries Jeyne Westerling, Walder takes the slight personally. While acting as if he's forgiven them, he lures them to their death at the wedding of Edmure and Roslin Frey (his daughter). He works with Tywin Lannister covertly to kill Robb and others at the wedding.
