Smalljon Umber

"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

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

Background
Smalljon Umber is the eldest son and the heir of Jon Umber. After his father's death, he becomes the new Lord of Last Hearth and head of House Umber. Although he dislikes House Bolton, he sides 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 surmising that Ramsay murdered him, despite his claims 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: Last Hearth is further north than any other castle, and it is always the Umbers who are forced to fight the wildlings, something Smalljon enjoys. This time, however, there are too many wildlings, and Smalljon requests Ramsays 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.

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 between Rains of Castamere and Oathbreaker.