Ivar is also attributed with the slaying of St. Edmund of East Anglia in 869 AD. By some accounts, when Edmund refused to become the vassal of a pagan, Ivar had Edmund bound to a tree, whereupon Vikings shot arrows into him until he died. According to others, he was shot in the nave of a church.
There is some disagreement as to the meaning of Ivar's epithet "Boneless." Some have suggested it was a euphemism for impotence or even a snake metaphor (he had a brother named Snake-in-the-Eye). However, the Scandinavian sources describe a condition that is sometimes understood as similar to a form of osteogenesis imperfecta (see below). The poem Háttalykill inn forni describes Ivar as being "without any bones at all".
Alternatively, the English word "bone" is cognate with the German word "Bein", meaning "leg". Apparently Ivar the Boneless was carried everywhere. So perhaps his epithet simply meant "legless" - perhaps literally or perhaps simply because he was lame.
It is possible that Ivar may be identical to the Ímar whose death appears in the Annals of Ulster in 873:
Ímar, king of the Norsemen of all Ireland and Britain, ended his life.
The story has it that when king Ælla of Northumberland had murdered their father, by throwing him into a snake-pit, Ivar's brothers tried to avenge their father, but were beaten. Ivar then went to king Ælla and said that he sought reconciliation. He only asked for as much land as he could cover with an ox's hide and swore never to wage war against Ælla. Then Ivar cut the ox's hide into so fine strands that he could envelope a large fortress (in an older saga it was York and according to a younger saga it was London) which he could take as his own. As he was the most generous of men, he attracted a great many warriors whom he consequently kept from Ælla when this king was attacked by Ivar's brothers for the second time.
Ælla was captured and, when the brothers were to decide how to give Ælla his just punishment, Ivar suggested that they carve the "blood eagle" on his back. According to popular belief, this meant that Ælla's back was cut open, the ribs pulled from his spine, and his lungs pulled out to form 'wings'.
In Ragnar Lodbrok's saga, there is an interesting prequel to the Battle of Hastings: it is told that before Ivar died in England, he ordered that his body be buried in a mound on the English Shore, saying that so long as his bones guarded that section of the coast, no enemy could invade there successfully. This prophecy held true, says the saga, until "when Vilhjalm bastard (William the Conqueror) came ashore[,] he went [to the burial site] and broke Ivar's mound and saw that [Ivar's] body had not decayed. Then [Vilhjalm] had a large pyre made [upon which Ivar's body was] burned.... Thereupon, [Vilhjalm proceeded with the landing invasion and achieved] the victory."
There are less extreme forms of this disease where the person affected can lack use of their legs, but be otherwise normal, as may have been the case for Ivar the Boneless. The disease is more commonly known as "Brittle bone disease."
In 2003 Nabil Shaban, a disability rights advocate with osteogenesis imperfecta, made the documentary The Strangest Viking for Channel 4's Secret History, in which he explored the possibility that Ivar the Boneless may have had the same condition as himself. It also demonstrated that someone with the condition was quite capable of using a longbow, and so could have taken part in battle, as Viking society would have expected a leader to do.