Rickard Karstark is the Lord of Karhold and the head of House Karstark, a vassal of House Stark
Rickard Karstark is the Lord of Karhold and the head of House Karstark, a vassal family to House Stark of Winterfell. He is a close ally and distant relation of House Stark. He has three sons, Torrhen Karstark Harrion Karstark, and Harald Karstark.
Lord Karstark listens to the debate between Robb Stark, Jonos Bracken and Greatjon Umber about whether they should join forces with Renly or Stannis Baratheon. When the Greatjon names Robb as the King in the North and lays his sword at his feet, Karstark is the second to join him, saying he'll have peace on those terms.
Rickard Karstark is among Robb Stark's host in the Westerlands and is present when Alton Lannister gives Queen Cersei Lannister's response to Robb's peace terms. Karstark's son Torrhen Karstark is later killed by Jaime Lannister during an escape attempt. After Jaime's recapture, Lord Rickard demands Jaime's execution in revenge for the murder of his son, but Catelyn Stark speaks for his life. After Lord Rickard's threatening reaction, she reminds him that he has sworn an oath of loyalty to Robb Stark and that Jaime is a prisoner of war. She says that he should remember who his king is and who she is. She promises him that Jaime will be punished for what he did. Reluctantly Lord Karstark gives in, but demands retribution when his King returns from The Crag. During the confrontation with Lady Catelyn, Lord Rickard also dismisses Talisa Maegyr as a "foreign bitch".
Catelyn sends Jaime to King's Landing with her sworn sword Brienne to exchange him for her captive daughters, fearing that Rickard or his men will kill him if he remains in the camp. He is furious that she has denied him his vengeance and rejects her argument that Jaime may yet save the lives of her children, adding that he personally would happily exchange his life for those of his deceased children, Torrhen and Harrion, even if it meant captivity for them. Robb tells Catelyn that she has betrayed him and orders her kept under guard.
Rickard's faith in Robb continues to deteriorate as the Northern host arrives at Harrenhal, finding the castle's inhabitants had been put to the sword. Roose Bolton attempts to reassure Rickard, telling him that he has sent his best hunter in pursuit of the Kingslayer, and that the dead will be avenged in time. Karstark, however, is clearly unconvinced.
Lord Karstark manifests his disapproval of the march to Riverrun for the funerals of Lord Hoster Tully, grandfather of his King, considering it a distraction from the war effort. When questioned by Robb if he has lost faith in the Northern cause, Lord Karstark insists that if the cause is revenge he will keep faith "until it snows in Dorne", but adds that he believes Robb lost the war the day he married Talisa Maegyr.
Rickard Karstark and his men kill Martyn Lannister and Willem Lannister in the dungeons of Riverrun and are brought before Robb Stark. He openly insults the King in the North and claims the war is a lost cause. Remaining true to his honor just like his father, Robb decides that Lord Karstark must die for his treason. Though Edmure Tully, Talisa, and Catelyn attempt to advise Robb to hold Karstark hostage and send him to the Night's Watch after the war - on the basis that the Karstarks form a significant portion of Robb's army, and they will abandon Robb if he executes their lord. Despite the warnings of all of his councilors, Robb refuses to listen.
As Lord Karstark is brought before Robb, he reminds him that the blood of the First Men run through both of their veins since they are of the North. Lord Karstark also reminds Robb he fought alongside Eddard Stark during Robert's Rebellion and alongside him against King Joffrey. Finally, he states that they are both kin, since House Karstark was founded by a Stark of Winterfell. Robb tells him that all of it didn't stop him from murdering the Lannister boys and it will not save him now. Rickard doesn't want to be saved, but he wants it to haunt him for the rest of his days. True to the traditions of the North and his father, Robb Stark personally beheads Rickard Karstark with a single strike of his sword after Rickard curses Robb and renounces all allegiance to him. In the aftermath, the Karstark forces abandon Robb and return home.
In the meantime, while he is being tortured in the Dreadfort, Theon Greyjoy incorrectly assumes Ramsay Snow to be Rickard's son, keeping him prisoner on Rickard's orders, since he is Robb's bannerman, remaining unaware that Rickard has been executed.
Rickard is mentioned by his last living son Harald Karstark when he meets with the Boltons at Winterfell. Karstark makes it clear that his house will never support the Starks again after Robb executed his father. Despite the fact that Roose avenged his father by killing Robb at the Red Wedding, Harald makes no attempt to intervene when Ramsay kills Roose after the birth of his half-brother, whom Ramsay also murders along with his stepmother Walda Bolton.
As head of House Karstark, an ancient family of the North that can trace its bloodline back to House Stark and the First Men, Lord Karstark readily answered Robb Stark's call when he raised his banners. His son died at the hands of Jaime Lannister, but Karstark's grief turned to fury when Catelyn Stark set the Kingslayer free. He was beheaded by King Robb when he killed two young Lannister hostages, and openly insulted Robb for marrying Talisa.