Even among the occasionally mercurial, well-drawn characters of History’s “Vikings,” Ivar the Boneless (Alex Høgh Andersen) stands out as a complex fellow. From moment to moment, Ivar can be needlessly cruel and domineering, or touchingly vulnerable. Born a cripple, Ivar has grown up cossetted by his mother Aslaug (Alyssa Sutherland) and mentored by Floki (Gustaf Skarsgård) in the absence of his father, Ragnar Lothbrok (Travis Fimmel). In the second half of Season 4, Ivar finally gets the alone time he’s always wanted with his father — though that means being tied to a ship’s mast in the middle of a squall and nearly drowned.

Historically, Ivar the Boneless was one of the most famous Vikings of all time, and showrunner Michael Hirst says we’ll see the beginning of Ivar’s glory days this season. Andersen, who is from a small town about an hour southwest of Copenhagen, called up Variety to discuss what makes Ivar tick.

Ivar spends so much time crawling around — does that take a physical toll on you?

My left wrist is really complaining, but that’s about it. The costume girls have done an outstanding job giving me special gloves. I’m really only crawling for a few meters for a few takes. I won’t complain. [Laughs]

They did give us a personal trainer when we first got here, and he literally killed us. I was crawling around the hotel room for the first few weeks.

 You originally went in to read for the other sons, but Michael Hirst asked you to read for Ivar.

All I can say is it was a sweaty experience. I was auditioning with 14 other guys for Ubbe and Hvitserk and Sigurd, not Ivar. They had a guy for Ivar. But something about the way I played the other sons made them ask me to read for Ivar. I didn’t know any of his scenes at all — so I was sitting there sweating, I’m trying to read the scene and remember it, and half an hour later Jordan [Patrick Smith], who got Ubbe, and I did our scene together, and we nailed it. Then, of course, when they turn on the camera, that red light goes on and you start forgetting everything. The third time was the lucky one.

Our first scene, where you see all the brothers together, that was our first scene together as well. We were sitting in the tent all nervous, four new guys, our first day. And this Irish dude comes up, it’s his 500th day on the show, and goes, “Welcome to the show, I just wanted to let you know the hundreds of people behind me don’t have a job next year if you f— up.” I’ve never laughed so nervously before in my life. But I really appreciate that he said it! Because it made us realize the weight of our work and the weight of our characters and the seriousness of the work.

How familiar were you with the sagas before this? Did you know Ivar’s history?

It’s interesting, because it is Danish heritage, and I do know some of the sagas. I could remember some of the stories Floki was telling. We had a comic book in Denmark called “Valhalla,” and I read it every time I had the chance. So I remembered the authentic stories from that comic book — Thor and Odin and Freya, I know all those stories.

But I have to say what I like about how Michael Hirst has approached Season 4B is how it’s a story about a family. And what I’m doing is not portraying a Viking — I’m portraying a human being with a disability in a society that is not okay with that. I’m trying to make him likable even though he’s a character who’s going to challenge the audience. He’s very religious and provocative, but first and foremost, he’s a vulnerable, angry, and sad kid. I hope the audience will remember where he came from and try to put themselves in his spot. I don’t think anybody who’s normal would be able to put themselves in his spot. It’s an awful life. I think he’s a little bit suicidal before Ragnar returns.

His father abandoned him, tried to kill him as a baby — so why does Ivar want to raid with Ragnar so badly?

Ivar needs a father figure. He has probably been the one of all the sons that needed Ragnar the most, and Ragnar has not been there. Ivar’s been the one sitting on the beach, observing his brothers being active, all that stuff. Because of that he’s become very intelligent. But I think that he sees and realizes he needs to do something, to go somewhere, to finally feel like a man. Going raiding with the most famous Viking of all time? He would rather choose five minutes of being a real man than a lifetime of pity. What eventually happens is Ragnar eventually succeeds giving Ivar some ambition and pushing him forward.

He may be a cripple, but Ivar can wield weapons pretty effectively. Is there a way for him to fight on horseback or something?

I can’t really reveal anything, but because Ivar is so intelligent, he’s going to be a great military strategist. Of course, we’ll never see him on the battlefield slaying Christians, but trust me, he’ll find his own way to do it. He’ll be the one standing on the hill organizing, which is also pretty cool, I have to say.

“Vikings” airs Wednesdays on History at 9/8c.