If you’re a fan of Vikings, the History channel’s ridiculously binge-worthy series, then you’re doubtless familiar with the name “Ivar the Boneless.” Just in case you’re not, here’s a little Ivar 101. Ivar the Boneless, aka Ivar Ragnarsson, was an actual historical figure. We know this both from his fame in Old Norse legends, where he was revered as a godlike warrior, and from British sources, which considered him a demon straight outta the depths of hell. The Norse Saga of Ragnar Lodbrok records that Ivar the Boneless was the son of the famed Viking warrior Ragnar Lodbrok and his wife Aslaug. Ivar cashed in on being born as the son of an already legendary father by going on to become one of the fiercest, most feared warriors in Viking history. But how much historical truth is there to the way his character is portrayed on Vikings? Let’s take a look at what history has to say about it.

What’s with the nickname?

As far as Ivar how came to be “boneless,” legend has it that there was a curse involved. See, his mom, Aslaug, was what we would refer to in modern times as something between a shaman and a witch. Well, the spirits apparently warned her that she and Ragnar needed to hold off on, um…celebrating his return from a long trip in the most intimate ways, for three nights. Ragnar, however, was feeling particularly amorous and gave no heed to his wife’s warnings. The myths reveal that the spirits were not amused and therefore caused Ivar, the fruit of their reunion, to be born “boneless.”

As far as what exactly “boneless” means, historians are not entirely sure. Ivar’s History channel character is depicted as being crippled, but whether or not that was actually the case is unknown Some historians suggest that he may have suffered from brittle bone disease, due to one passage that states, “Only cartilage was where bone should have been, but otherwise, he grew tall and handsome and in wisdom, he was the best of their children.” Others think that his nickname may have been more of a jab at his impotence because he was said to have “no love lust in him.” This may not stack up, however, given that he was recorded as having several children.

Then there’s another very different but really interesting theory. Back in the 17th century, a farmer discovered the remains of a nine foot tall Viking warrior that some have theorized may have been Ivar the Boneless. The theory is backed by the fact that Ivar was famous for his massive size and that the skeleton was reported to be about nine feet tall. The tallest guy in recent history was a man named Robert Wadlow, who stood at 8′ 11″ and did indeed need braces to stand due to his enormous height. Whatever the case, we may never know for sure why exactly Ivar was considered “boneless,” but what we do know for sure is that he did not play on the battlefield.

Rise of the heathens

While Norse legends describe Ivar as being as huge as a bear, they also note that he was as cunning as a fox, making him a truly formidable opponent. From what history tells us, there was not so much turmoil between Ivar and his brothers as the show Vikings would have us believe. On the contrary, his brothers appeared to highly respect their boneless brother and rarely made strategic decisions without consulting him. Given that he was highly loyal to his family, he did not take the news well when he found out that King Ælla of Northumbria had killed his father, Ragnar, by tossing him into a pit of vipers. In fact, he demanded to know every detail of his father’s death so he could plot his revenge while seething with as much hatred as possible.

Ultimately, he decided to form the Great Heathen Army, as the English would come to call them and exact his revenge on Northumbria. Legends of the battle recount that Ivar fought along with the warriors he led while hoasted atop a shield held by his warriors. If this was because he was crippled, then he definitely didn’t let his health issues slow him down in the slightest. Ivar eventually took the city and then executed King Ælla in the world’s most excruciating way. He performed the dreaded “blood eagle” on the king, ripped open his ribcage from the back, and pulled out his lungs, sprinkling salt into the wounds for added effect.

Ivar takes England

Since Ivar was already nice and riled, he decided that there was no need to stop with King Ælla’s puny kingdom. Instead, he decided to take an army of his closet heathen friends and see what kind of trouble they could stir up in the rest of England. As Simeon of Durham, an English writer of the time, would later put it, “The army raided here and there and filled every place with bloodshed and sorrow.”

Amid all the territories of England at the time, the strongpoint was the kingdom of Mercia. So Merica, of course, was where Ivar and his armies went. It took them about a year of carefully plotted attacks, but ultimately they were able to overtake the city of Nottingham and give almost everyone inside a one way trip to the afterlife. After that, England was pretty much at the mercy of the Viking invaders and by 870 AD,  Ivar the Boneless conquered territories stretched from Britain to Dublin.

How did Ivar the Boneless die?

Ivar’s end came unexpectedly around 873 when the Annals of Ireland report that, “The Norwegian king…died of a sudden hideous disease.” Despite the tough break, Ivar the Boneless would doubtless be pleased that his legacy has managed to live on to this day.