Ser Rodrik Cassel is Master-at-Arms at Winterfell and a loyal servant to House Stark. Even in his old age he is still a skilled warrior. He was executed by Theon Greyjoy during the fall of Winterfell.
Ser Rodrik Cassel is Master-at-Arms at Winterfell and has trained many of its soldiers in the art of combat, as well as Robb Stark, Theon Greyjoy and Jon Snow. He is the primary military advisor to House Stark of Winterfell. House Stark are Lords Paramount of the North. The North is one of the constituent regions of the Seven Kingdoms and House Stark is one of the Great Houses of the realm.
Rodrik is a knight, which is somewhat unusual in the North where most of the population holds to the Old Gods of the Forest. He fought in Robert's Rebellion and is an old friend of both Lord Eddard Stark and Greatjon Umber, the Lord of Last Hearth. His nephew Jory Cassel also fought in the rebellion and is the Captain of the guards at Winterfell.
Ser Rodrik informs Lord Eddard Stark that Will, a deserter from the Night's Watch, has been caught in the hills. He accompanies Eddard to Will's execution. On the way back to Winterfell he witnesses the discovery of the six direwolf pups in the Wolfswood. The Stark children adopt the pups. King Robert Baratheon visits Winterfell and Ser Rodrik assembles with the rest of the household to welcome him. Robert asks Eddard to serve as hand of the King. Bran Stark is found severely injured at the base of a disused tower. Eddard goes south to King's Landing and Jory accompanies him as the Captain of his personal guard while Rodrik remains in Winterfell. An assassin infiltrates the castle and attempts to kill Bran but is foiled by Catelyn and Bran's direwolf Summer. Rodrik identifies the blade carried by the assassin as Valyrian steel. Catelyn suspects House Lannister and decides to warn Eddard personally. Rodrik offers to send a squad of guards with her but she is concerned about drawing attention. He offers to accompany her personally and she agrees.
Rodrik and Catelyn arrive in King's Landing. He escorts her during through the city and they are told that Littlefinger lost the blade used by the assassin gambling with Tyrion Lannister. They set out for Winterfell. At the Crossroads Inn, Rodrik unsuccessfully attempts to dismiss the singer Marillion. He helps Catelyn take Tyrion Lannister prisoner when he arrives at the inn.
They head east through the Vale of Arryn. Rodrik helps fend off an attack by the hill tribes and receives a minor wound, but is able to complete the journey to the Eyrie. Rodrik's nephew Jory Cassel is killed by Jaime Lannister while protecting Eddard in King's Landing.
Rodrik witnesses Tyrion's trial by combat and is disappointed when Tyrion's champion wins. King Robert dies following a hunting mishap and Eddard questions the lineage of his successor Joffrey Baratheon. Eddard is arrested for treason and held in the dungeons of King's Landing. Rodrik accompanies Catelyn to Moat Cailin where they find Robb Stark's army camped. Robb needs to cross the river trident but is unsure of the support of Lord Walder Frey. Rodrik advises Catelyn to not go into the Twins alone to talk to Lord Frey. She does so anyway and negotiates safe passage. Robb wins a victory in the Battle of the Whispering Wood and captures Jaime. News of Eddard's execution reaches the camp and Rodrik is part of the group that proclaims Robb Stark the King in the North.
Ser Rodrik is present when King Robb presents Ser Alton Lannister the peace terms he must deliver to the Iron Throne. Robb sends Ser Rodrik back to Winterfell to keep Bran and Rickon safe while Catelyn goes to the Stormlands to treat with King Renly Baratheon.
Ser Rodrik enters the Great Hall of Winterfell calling for Bran. He reports that Torrhen’s Square is under siege. Maester Luwin is shocked, remarking that Torrhen’s Square is just 14 leagues away and wonders how the Lannisters have reached so far north. Osha listens intently as she lights candles at the back of the room. Ser Rodrik speculates that it could be a raiding party led by the Mountain or a group of sellswords. Bran says that they must help their bannermen. Rodrik nods agreement and says that even with most of their forces fighting for Robb he can gather 200 decent men. Luwin wonders if Rodrik needs to take so many and Bran cautions that they must protect their bannermen if they expect their bannermen to protect them. Rodrik smiles at the boy’s wisdom and Bran orders him to leave as soon as he has his men. Rodrik confidently says that it will not take long because southerners do not do well in their territory.
Theon Greyjoy planned the siege as a diversion and invades the poorly defended Winterfell while Rodrik is away. Rodrik is caught on his way back from Torrhen's Square. He managed to cut down two of Theon's men, before being disarmed by Black Lorren
He is dragged into Winterfell in a fury at Theon the traitor. Theon is going to have him thrown in the dungeon, but when Ser Rodrik spits in Theon face, Dagmer says he must sentenced to death (Theon's men will lose respect for him otherwise). Bran is distraught since Theon had promised earlier that no-one would be harmed if they surrendered. Ser Rodrik tells Bran to be calm, saying "I'm off to see your father." He reminds Theon that at Winterfell, the man who passes the sentence swings the blade. Theon botches the execution and it takes three sword strikes and a kick to finally behead Ser Rodrik, to the horror of onlookers.
Winterfell's Master at Arms, Ser Rodrik serves as the Starks' primary military and security adviser. He was stoppily beheaded by Theon Greyjoy.