The Umbers are led by Lord Jon "Greatjon" Umber, a giant, fierce warrior. They will never betray their Stark overlords. In fact, our spies reported that a quarrel over position in the Northern army emerged between Robb Stark and the Greatjon during which the Greatjon drew his sword. Robb's direwolf charged him and bit off two of the Greatjon's fingers. Lord Umber laughed this off and from this point on has been the young usurper's greatest champion. If the loss of two fingers cannot effect his loyalties, what hope do we have with bags of gold.