Jarl Borg is a powerful and important leader in Götaland. Subsequent to becoming Jarl after his father's death, his brother, with whom he'd been close, sought to usurp his power and title. When Borg threw a feast to celebrate his marriage, his brother attempted to poison him. The Jarl survived only because his new bride drained the cup intended for him. Borg claims he is never able to forget his wife's death-screams as a result. He punished his brother by blinding him, then burning him alive. He tattooed his body with several symbols, including a stone mask on his back.
Jarl Borg becomes embroiled in a dispute with King Horik over mineral-rich lands that they both desire to control. In an effort to resolve the dispute, Horik sends Ragnar Lothbrok as his emissary. Seemingly unimpressed by Ragnar's reputation, Jarl Borg refuses to relinquish his claim, regarding Horik as a foreign king with no legitimate claim to the disputed lands. Unwilling to negotiate or compromise, he insists that he will neither renounce his claim nor accept the King's payment for doing so. While waiting for further word from King Horik, Ragnar is persuaded by Jarl Borg to take the opportunity to visit Yggdrasil, the tree of life in Nordic mythology. In Ragnar's absence, Jarl Borg seeks to entice and manipulate Rollo into betraying his brother. Preying on Rollo's resentment and insecurities, Jarl Borg succeeds at making Rollo his ally.
The Battle of the Brothers starts. Alongside Rollo, Jarl Borg fights against the united forces of Ragnar and King Horik. The battle ends when Rollo gives up as a result of being unwilling to fight Ragnar himself. During the assembly that follows, Borg and Horik continue to argue, only to be stopped by Ragnar and his speech about raiding the West. Persuaded, Borg and Horik finally agree on terms, in addition to raiding together someday.
Four years later, Borg travels to Kattegat, eager to raid together with the others. King Horik, however, still finds himself unable to trust him, so he has Ragnar exclude him from their plans. Jarl Borg becomes infuriated when he finds out that Ragnar and Horik have decided to break their agreement. He consequently even tries to coax Rollo into betraying Ragnar again, though he fails.
At the feast of his wedding to Torvi, Jarl Borg announces that they will be attacking Kattegat in retaliation for Ragnar and Rollo's betrayal. Although he blames King Horik more, he wishes to take advantage of the vulnerability of Kattegat. Borg's ships sail up the fjord to Kattegat, with Borg fighting his way into the town, wielding an axe in each hand. The attack is a success, killing most of the town's defenders. Borg seeks Rollo, intent on vengeance for his treachery and blaming him for putting them in their situations in the first place. Though Rollo escapes, Jarl Borg revels in his victory, mirthfully entering Ragnar's Hall. When he goes to the Seer for a reading, the Seer predicts an eagle in his future. Borg's wife Torvi soon becomes pregnant.
While in England, Ragnar receives word of the attack on Kattegat. As a result he returns to Scandinavia. Jarl Borg is ecstatic upon hearing of Ragnar's return, looking forward to fighting and defeating him. Unbeknownst to him, Ragnar had since received support and reinforcements from his son Bjorn and ex-wife Lagertha. In the night, they sneak into the village to burn the winter supplies of grain. Jarl Borg, enraged by this attack and taking the bait, is drawn out of Kattegat with his forces to hunt down those responsible for the intrusion, only to be confronted by Ragnar and his men and allies. After a brief but fierce battle with casualties on both sides, Jarl Borg escapes with his remaining men, retreating from Kattegat.
After their attack on Wessex, the forces of Horik are greatly reduced. Horik advises Ragnar to reestablish their alliance with Jarl Borg, who has enough ships and men to allow them to successfully raid in the West again. At Horik's suggestion, Ragnar sends Rollo to Jarl Borg with the proposal. Borg, after consulting with the skull of his dead first wife, accepts Ragnar's offer and soon comes to Kattegat with his ships and men. That night, Rollo has the barn sheltering Borg's forces set on fire and captures Jarl Borg, having him savagely beaten, without informing King Horik. Ragnar has Borg brought into the Great Hall and, barely containing his vengeful fury, informs him that, for threatening his family, he'll be subjected to the blood eagle, an honorable yet brutal execution allowing for the passage to Valhalla.
Jarl Borg is held captive in Kattegat awaiting execution. King Horik tries change Ragnar's mind about executing Borg, as they need his men and ships to attack Wessex. Ragnar, however, has sent word out, requesting other allies to replace Jarl Borg in their alliance. King Horik, with the help of Siggy, secretly visits Jarl Borg. Borg proposes a deal in which Horik would help Borg escape so he can kill Ragnar, who, Borg argues, seems to have the ambition to rise above being earl, possibly even replacing Horik as king. King Horik agrees to Jarl Borg's proposal and states that he knows of men who wish to challenge Ranger who are willing to help Jarl Borg escape execution. However, Ragnar's former wife Lagertha, now an earl herself, arrives as a new ally with four ships and around one hundred warriors. Having no use for Borg anymore, King Horik voices no further objection to Jarl Borg's execution. He allows Borg to continue to hope, however, since hope would make death even more horrible.
Someone enters Jarl Borg's cell in Kattegat, late at night. At first, Borg thinks it's King Horik coming to free him. Unshackled, Jarl Borg exits his cell, carrying the skull of his late first wife, thinking his escape is at hand. Emerging into the torchlit center of Kattegat, Borg's hopes are dashed. The entire population of Kattegat awaits. Seeing that no hope of escaping his fate exists, Borg is seemingly resigned to the inevitable.
Kattegat is decked out in barbaric splendor for the grim spectacle. Drums beat and mounted skulls seem to grin mockingly in the flickering torchlight as the doomed jarl approaches a platform erected in the center of the village. Waiting on the platform is a grim-faced Ragnar, clad in a long, white tunic, not a trace of mercy in his icy eyes.
Removing his cloak, Borg throws the garment to his pregnant wife, Torvi. Assuming the position between two posts, Borg places the skull of his late first wife on one of the posts, then kneels. Ragnar starts with a skinning knife, opening Borg's back up the spine. The planks of the platform are soon slick with the blood of the jarl. With the flesh of the back laid wide open, Ragnar takes a hatchet and proceeds to hack the ribs away from their moorings on either side of the spinal column causing the rib cage to spring open and expose the lungs. During the process, overcome with the grief and horror of her husband's suffering and imminent death, Borg's wife, laden with the unborn child the jarl will never see, faints to the ground. Taking Borg's lungs in his hands and drawing them from the gaping chest cavity, Ragnar drapes them over the stoically-suffering jarl's shoulders.
Without the diaphragm to expand and contract the lungs, the jarl of Götaland dies not long thereafter from suffocation. The last sight Jarl Borg sees as the darkness of death descends is an eagle, a pet of Ragnar's, perched nearby. Jarl Borg smiles as the eagle returns his gaze. Having endured his torturous, horrific death without so much as uttering a cry, Jarl Borg, a Viking to the last, proves himself worthy of Valhalla.
Jarl Borg is a fearsome warrior, cunning tactician, intelligent, manipulative, and a powerful Jarl. He is a force to be reckoned with. He is a rival to King Horik for the lands of Götaland. The two men intensely hate each other. Borg seeks to better his kingdom's position, whatever the cost. Despite these traits, he is a rather civil person overall. He is deceitful and sows dissension and betrayal amongst his enemies. He senses Rollo's deep resentment and envy of Ragnar's growing fame, and uses Rollo's feelings to his own advantage. He uses his cunning and intelligence, more than brute force, during battles and fights. He often observes the battle and makes strategic decisions rather than simply throwing himself into the fight. Decades after his death, Torvi and Bjorn both still remember him as a great warrior worthy of respect, and they speak positively of him to his son.
- Jarl Borg not only listens to the advice of his beloved first wife's skull, he also lovingly strokes it. At one point, he gives it a somewhat one-sided French kiss.
- Jarl Borg is not the ruler of Götaland, but specified as one of several earls/jarls of Götaland.
- Jarl Borg belongs to a distinctive Norse tribe known as the Gautar, a people referred to in English works such as Beowulf and Widsith as the "Geats," and related to the Germanic Goth tribes which invaded the western Roman Empire. The Geats have since been assimilated by the Swedes in the late-Viking and early-Medieval periods.
- Jarl Borg, as a powerful Geatish lord of near-kingly powers, may have been a member of the royal clan of the Wulfings (descendents of the wolf) who traditionally ruled over the Geats of Ostergotland.
- In the episode Eye For An Eye, Jarl Borg visits the Seer asking for his prophecy. The Seer tells him that an eagle hovers above him, but simultaneously he is the eagle. Jarl Borg takes this as a good sign, as eagles are signs of good fortune. The Seer cryptically remains silent, neither confirming nor denying this. The Seer's prophecy is shown to be negative for Jarl Borg. When the Seer said he was an eagle, he was referring to how Jarl Borg would look like one after suffering the blood eagle. The eagle hovering over him could also be a reference to Ragnar, as Ragnar executed Borg while his pet eagle watched.
- Jarl Borg was originally supposed to be a Swedish Jarl, living in Sweden. But Swedish actor Gustaf Skarsgård, who plays Floki, told Michael Hirst that "Sweden" did not exist as such in the time of the Vikings and that Uppsala would be located within it if it did. Hirst then changed Borg to a Geatish jarl, since there would not be any motivation for Ragnar going home to Kattegat before visiting Borg if he was already in Svealand (literally, "Land of the Swedes").
|Season one appearances|
|Rites of Passage||Wrath of the Northmen||Dispossessed|
|Trial||Raid||Burial of the Dead|
|A King's Ransom||Sacrifice||All Change|
|Season two appearances|
|Brother's War||Invasion||Treachery||Eye For an Eye||Answers in Blood|
|Unforgiven||Blood Eagle||Boneless||The Choice||The Lord's Prayer|