Smalljon Umber

Jon Umber, commonly called Smalljon Umber, was a recurring character in the sixth season, debuting in "Oathbreaker". He was played by Dean S. Jagger. Smalljon was the son of Greatjon Umber, and was the Lord of Last Hearth.

Background
Smalljon Umber was the eldest son and heir of Jon Umber. After his father's death, he became the new Lord of Last Hearth and head of House Umber. Although he disliked House Bolton, he sided with Ramsay Bolton to protect the North against the wildlings.

Season 6
Smalljon Umber travels to Winterfell to treat with Ramsay Bolton, requesting aid to fight the wildlings that have been let into the North by Jon Snow. Ramsay questions his motives, since the Umbers are famously loyal to House Stark, but Smalljon notes that House Karstark has Stark blood, yet Harald Karstark is Ramsay's new lieutenant. Smalljon calls Ramsay's father Roose a cunt, and when Ramsay attempts to praise Roose, he interrupts him, again calling him a cunt, and correctly accuses Ramsay of murdering him, despite Ramsay's persistent claim that Roose was poisoned by his enemies.

Smalljon reveals that Jon Snow has let a wildling army south of the Wall, which is bad news for the Umbers as Last Hearth is further north than any other castle, and it is always the Umbers who are forced to fight the wildlings first, something Smalljon enjoys. This time, however, there are too many wildlings, and Smalljon requests Ramsay's help. Smalljon refuses to swear fealty to Ramsay, or even kneel. Instead, he presents Ramsay with the captives Osha and Rickon Stark. When Ramsay asks Smalljon how he knows the boy is really Rickon Stark, he provides the severed head of Rickon's direwolf, Shaggydog, as proof.

Smalljon, Ramsay, and Harald attend a parley with Jon Snow, Sansa Stark, and Davos Seaworth, offering terms for surrender. When Sansa asks for proof that Ramsay has Rickon, Smalljon tosses Shaggydog's head onto the ground. He and his soldiers take part in the Second Battle of Winterfell, where he watches as Ramsay leads a leashed Rickon onto the battlefield. Smalljon leads the Bolton spearmen who form a wall around the Stark army, rallying them with a cry of "Who owns the North? We do!" After the Stark army is surrounded by the spearmen, Smalljon climbs the wall of bodies to fight in the circle, beginning by slaying an injured wildling who was attempting to escape. He fights his way to Jon Snow, but is swept away by the crowd before they can fight. He then comes face to face with Tormund, who he beats into submission with his fists and his own head, despite becoming trapped and crushed within the Stark army. Before he can finish off Tormund, he is momentarily distracted by the arrival of the Knights of the Vale, giving Tormund enough time to bite into his neck and tear out his throat and then repeatedly stab him in the face.

Quotes
"Your father was a cunt, and that's why you killed him. I might have done the same to my father if he had not done me the favor of dying on his own."

- Smalljon Umber to Ramsay Bolton

In the books
In the A Song of Ice and Fire novels, Jon Umber is nicknamed "Smalljon" for the sake of differentiating him from his father Greatjon Umber. However, "Smalljon" is nicknamed to denote his younger age, not a reference to his size - he is in fact almost as large as his father and is noted to still be growing and may even end up larger than his father.

In the books, the Smalljon is killed by Bolton men while defending Robb Stark at the Red Wedding. Due to Robb's bannermen trusting the holy bond of guest right that Walder Frey had promised, Smalljon was left unarmed at the wedding feast tables. Unlike his father, he did not drink, because he was assigned as one of Robb's bodyguards that night. As the massacre began, Smalljon's first priority was to protect his king: he wrestled a table off its trestles and used it to shield Robb, then bludgeoned Ser Raymund Frey across the face with a leg of mutton and made a run for his swordbelt at the end of the hall, but was hit halfway through by one of the crossbowmen in the balcony who had been disguised as musicians. Smalljon fell to his knees, and one fully armed Bolton soldier then finished him off, decapitating him with two strokes of an axe.

Given that Smalljon wasn't introduced at the time of the Red Wedding, he is presented as alive in the TV continuity. Greatjon Umber does have other, surviving sons in the novels, however (though they haven't been named), so the TV series apparently simply condensed them together. Also in the novels, after the Red Wedding, the surviving leaders of the surviving Umber forces (which consist of the eldery and the green boys) at Last Hearth are Greatjon's uncles, Mors "Crowfood" Umber and Hother "Whoresbane" Umber, who have to deal with the new Bolton rule of the North: the former joins Stannis, and the latter reluctantly joins the Boltons. They may have also been condensed into Smalljon.

In the novels, Greatjon was taken alive as a prisoner during the Red Wedding, because as the head of one of the major noble Houses from the North he was a valuable hostage, and he remains a prisoner at the Twins. In the TV series Greatjon didn't appear after Season 1 due to the actor being unavailable (it isn't clear why they didn't simply recast the role given that Greatjon wouldn't appear after Season 3 anyway). Writer Bryan Cogman, however, has remarked via twitter that Greatjon wasn't at the Red Wedding because he was off commanding other armies in the Riverlands, and he remained free and uncaptured in the TV continuity. However, he was confirmed to be deceased in Season 6, meaning that he died sometime after the events of the third season.

Smalljon's death in the television series puts him back in sync with his novel counterpart's status.