Conceived after his father's return from England, Aslaug had been giving Ragnar several counsels, forewarning things to come. Aslaug had warned that they should not have sex for at least three days, knowing of a prophecy that threatened the prospective child's health, but Ragnar insisted. Because Ragnar did not heed her warnings, Ivar was born with weak bones, his legs twisted and seemingly broken, hence the nickname "Boneless".
When he was born, Aslaug and Ragnar feared for his difficult life. Ragnar, as well as Siggy, suggested that Ivar should be killed, though Aslaug refused. Ragnar once took him out in an attempt to kill him himself; however, Ragnar could not bring himself to do so. When Aslaug told Ragnar his name, Ragnar gave him the epithet "Boneless".
Ivar was tormented with pain, but Ragnar did not care much. Later Harbard seemed to be able to ease Ivar's pain through unknown means. When Harbard left he claimed to have taken some of Ivar's pain into himself and that Ivar would not suffer as much in the future.
Ivar was seen when he was playing with his brothers in Kattegat while being carried in a cart which Ivar tells them not to break his bones. Later he was greeted by Bjorn who just came back from Paris and later in the episode. He said goodbye to Bjorn and he told them to take care of Ragnar. In Yol, Ragnar attempts to involve Ivar in the celebration of Yol and hang a piece of mistletoe as a ornament. Ivar refused and Aslaug took him away from Ragnar. Aslaug stated that Ivar was not like Ragnar and her responsibility, not his. Ragnar said he loved Ivar as much as Aslaug, to which Aslaug replied he did not act like it. Ivar later was brought to Floki by Aslaug to be mentored in the path of a Viking, with Aslaug intending for her son to hate the Christians. Floki seems to bond with Ivar, as they are fellow outcasts.
While Ivar is learning from Floki, he sees various children playing and wants to join them, so Floki puts him in his cart and takes him out among them. Ivar is mostly ignored by the other children despite his pleas for them to toss him the ball, so Floki catches it and tosses it to him. Another child runs up and tries to wrestle it away from Ivar; unable to overcome him in strength, Ivar impulsively picks up a hatchet in his cart and strikes the boy in the head, mortally wounding him. Ivar is horrified; Aslaug hastily comes over to him and tells him it was not his fault.
Years later, in The Last Ship, Ivar defends his father's honour from his brothers, who criticize Ragnar for abandoning them for so many years. Ivar also justifies Ragnar keeping the destruction of their Wessex settlement a secret, stating that the fame from invading Paris (city) was more important. Ivar is later seen greeting Ragnar when he returns.
Ivar is shown to be impotent when his brothers set him up to have sex with a slave girl. The slave girl tells him that potency is not as important as other characteristics. He later has a conversation with Ragnar in which Ragnar asks him to go to England. All other brothers have declined Ragnars invitation to go, but Ivar says he will go.
As a seer-woman, Aslaug had warned Ivar not to go England, as he would die in a storm. Ivar dismissed this, as he was intent to learn from his esteemed father, and get to know him as a father more than a King. Prior to leaving, with some Saxon gold that Ragnar gave him, he got a town blacksmith to make him a metallic contraption, which enabled him to walk more ably than before. He surprised his parents and brothers with this, and set forth with Ragnar to England.
Ragnar had bribed his former subjects into raiding with him, even those who publicly expressed their hatred of him. They took some ships that Bjorn had lent to them, and pursued across the North Sea to England. Despite an initially calm crossing, they had encountered a heavy storm on the horizon. Once the storm hit, some ships were lost, and they were capsized by a large wave. Aslaug was able to see this, as a seer, and was immensely distraught at her son's apparent death.
However, Ivar and Ragnar, and some of the raiding party, survived. They gathered on a beach, and found a nearby cave to settle in and reformulate a strategy. Ivar's metallic "legs" were also lost in the storm, and his father told him to crawl. However, this was not out of cruelty, as he said this weakness was also his greatest strength.
The party lived off the land for several days, narrowly averting detection by an English girl collecting forest produce for her town or village. Ivar asked Ragnar why he left the kingship, but he did not respond. He did however say that coming to England was his destiny.
At the end of Season Four, his father is avenged and he kills Sigurd because he insulted him one more time (saying that he never likes Aslaug, their mother).
From birth, Ivar has been subjected to intense pains due to his physical condition, resulting in him receiving very different treatment than the rest of his brothers. Ivar is shown to be very selfish and cruel even showing signs of sadistic and psychopathic tendencies, as he laughs when he learns of Siggy's death, and does not care about the settlers slain in Wessex, even his own brothers refer Ivar as "Crazy". Having been mentored by Floki from a young age, Ivar shares his hatred for Christianity. Ivar admires his father for his great fame and successful raids. Ivar deeply loved his mother, and after her death he is only close to Ubbe and Floki.
Ivar also has a keen mind, and immense upper body strength, as account for having to literally crawl in most cases. During the invasions of England to avenge their father, he impressed his brothers and the other Norsemen with his tactical acumen. He shows devotion to his family, and his people, though had a long-running and eventually fatal fued with his elder brother, Sigurd.
- As of the Season 2 finale, Ivar and his brothers would be known by the Old Norse title of Budlungr or 'prince'.
- Ivar hinn Beinlausi (Ivar the Boneless) is the Old Norse rendering of his name.
- It has been suggested that the historical Ivar suffered from brittle bone disease which rendered his legs useless. In most modern Scandinavian languages the word for "bone" is the same as the word for "leg". The disease also causes Ivar's sclerae (the whites of the eye) to have a blueish hue. However, this is disputed, since there are bones uncovered from Derbyshire in England (where the town of Repton is situated), which are supposedly his own. The skeletal remains show a man of above average height and size, who despite this had a healthy skeletal system.
- Most accounts of Ivar describe him as either incredibly cruel or incredibly wise, or both.
- The King of East Anglia, Edmund the Martyr, was said to have been shot with arrows and beheaded by Ivar, as punishment for refusing to renounce Christianity. This is said to have been near the current English town of Bury St. Edmunds, which was named after him in tribute.
- Ivar is said to have been one of the first Norse kings of Dublin in Ireland.
- Ivar is accounted as being the son who defeated and blood-eagled King Aelle in retribution for his fathers death.
- Due to his disease, Ivar suffers from sexual impotence, this is mentioned by Margrethe after they tried to have sex.
- The idea of a lame viking being tied to a chariot to enter battle comes from the legendary danish king Harald Wartooth, who due his old age, was tied to a chariot at the Battle of Bråvalla in order to face his enemies.
|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|
|Season three appearances|
|Mercenary||The Wanderer||Warrior's Fate||Scarred||The Usurper|
|Born Again||Paris||To the Gates!||Breaking Point||The Dead|
|Season four appearances|
|A Good Treason||Kill the Queen||Mercy||Yol||Promised|
|What Might Have Been||The Profit and the Loss||Portage||Death All 'Round||The Last Ship|
|The Outsider||The Vision||Two Journeys||In the Uncertain Hour Before the Morning||All His Angels|
|Crossings||The Great Army||Revenge||On the Eve||The Reckoning|