SPOILER ALERT: Do not read if you have not yet watched “The Lost Moment,” the Dec. 19 episode of “Vikings.”

Given that the series revolves largely around issues of power struggles, raiding and war, “Vikings” has never treaded lightly in terms of killing off notable characters and actors. But as the series continues its next-generation exploration of Ragnar Lothbrok’s sons in a post-Ragnar world, even the rules it previously established have been shaken up with the latest character death.

In “The Lost Moment,” new ruler Ivar the Boneless (Alex Hogh Andersen) continued his quest to convince himself and others in Kattegat of his divinity after controversially sacrificing a young woman he presented to his followers as Lagertha (Katheryn Winnick). However, when he visited The Seer (John Kavanagh) to confirm his newfound self-appointed power status, the prophecies weren’t exactly foretold in his favor. And so, in a heated and impulsive moment, Ivar put his axe through The Seer’s head, killing the one character on the series that has always been untouchable.

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“It raises the question, can you actually ever kill a man who is possibly dead already?” creator Michael Hirst tells Variety. “It’s huge for the people immediately around Ivar. To me, it was more to do with what Ivar felt that he was capable of doing as the supreme ruler. What he does or tries to do is so shocking and unexpected that it says more about Ivar’s ambitions and what’s happening in Ivar’s head.”

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Here, Hirst breaks down the show’s latest casualty, what it means for those in Kattegat and for the Vikings as a whole, and how this affects the already tense relationship between Ivar and his brother Hvitserk (Marco Ilso).

At what point did you know it was time for The Seer to exit?

When I started writing about what Ivar would do when he became king of Kattegat and what he would do once he was persuaded — or helped convince himself — that he was special. He persuades himself that he is a god, although I’ve never assured myself that he totally believes that. But once I’d established that idea I had to imagine the kinds of things he might do if he believed himself to be totally different from other men and possibly a god. One of the things we know is he’s capable of is lashing out at people and losing his temper and being impulsive. He killed one of his own brothers, obviously, earlier in the show.

It came to me one day that he might do the impossible sin of killing, or at least trying to kill, The Seer because he couldn’t bear to feel that someone was laughing at him or didn’t believe this idea that he might be divine. So that became essential to my portrait of him as a ruler and how far he would dare to go — to kill one of the most iconic characters in the Vikings world. It was shocking to me when I thought of it, which is always a nice feeling to have. Do I dare to do this? What are the consequences of doing it? I’ve lived with The Seer for so long. But then it was the logical thing, the perfect thing for Ivar to do, to celebrate his own divinity.

The Seer’s prophecies have driven a lot of the characters’ motivations over the seasons, so does his removal shift the series?

The death, or possible death, of The Seer doesn’t actually shift the show because The Seer is not an active participant; he just foresees and fore-suffers everything. His memory is long enough to know things from the start and envision things moving forward. If he’s lost, it’s only that voice of prophecy and conscious perhaps that is lost for the Vikings. It’s a huge spiritual loss, which Hvitserk voices. He says, “Look what you’ve done. You’ve cut the head off our tribe. You’ve removed the conscious of the Vikings. You’ve removed the person who understands and tells our story.” So it’s huge in that sense.

Does the storyline open up another connection to the Gods or how prophecies are foretold moving forward?

My point is that actually you can’t kill The Seer because The Seer is already dead. He is in a half-life between life and death. However…Ivar thinks he’s killed The Seer [but] he may not have killed him because The Seer isn’t mortal in the way other men are mortal. He may appear in different guises or in the future in different ways. But I don’t think a human — even a demigod as Ivar now claims to be — I don’t think they’re capable of removing the conscious or spiritual guide that’s been there since the beginning of time and will probably be there until the end of the Vikings age.

Did John Kavanagh have any input or was there any conversation surrounding The Seer’s demise from a creative standpoint?

I’ve never discussed anything with John because I knew that he would know. He’s The Seer! I’d worked with John before: he was a great Roman-Catholic bishop in “The Tudors,” with an absolutely wonderful voice — a great stage actor, by the way. So, he was the perfect Seer because you don’t really see his face; it’s his voice you recognize more than anything else, so I wanted John. It was established as a convention early on that with all the other actors I discuss their roles and motivations, but I didn’t need to do that with John. His role is just prescribed. He’s The Seer. He’s the voice. He’s, as I say, the conscious of the tribe. So we never discussed it and he never once came to me and asked what something meant or why he was saying something. He accepted everything that I gave him to say, however obscure, and somehow he made sense of it in the way he spoke the lines. He found a way of interpreting these strange sentences. We had a strange relationship — I would say hello to him in the morning when he came on set and he never asked me a question and I never offered him an explanation of what the lines were. He would just do the music. John as a great actor was more concerned with the rhythm of the words than their necessary meaning.

Will there be tangible repercussions in Kattegat?

Ivar is ashamed, very quickly, which is typical of Ivar. Like, he kills his brother and then asks for forgiveness and tells you he never meant to do it. Part of you believes he didn’t mean to do it, but part of you probably thinks he always did mean to do it. When he was a little boy he killed another little boy just over a game they were playing. He understands very quickly the enormity of what he’s done and he tries to burn the body. But there are some things you cannot wash away and wish away and it’s like the voice of The Seer, he’s not quite human so he’s in a different sort of space. Ivar cannot ultimately escape the voice of conscious. He can’t escape — no one can escape — the prophet, The Seer, the one who will always be looking over Viking affairs and making prophecies and suffering over everything that happens in the show. For me it’s a complex idea, but I would say that Ivar kills The Seer and at the same time he doesn’t kill The Seer because he can’t.

What does this plot point mean for the relationship between Ivar and Hvitserk?

The relationship is a deep and complex one. I spent episodes and seasons exploring and discovering what that relationship actually is about. Hvitserk does this amazing thing and jumps ship [to join Ivar] despite it being more logical for him to stay with Ubbe [Jordan Patrick Smith]. Ever afterwards Hvitserk is trying to understand why he did that. He doesn’t know if the Gods intended him to do that. He’s in a complicated relationship both with his own psychology and with Ivar. And both of them actually — both Ivar and Hvitserk — try and work out what their relationship means and why they are bound together. In due course they start to think they’re bound together because the Gods mean one of them to kill the other. And that’s why Hvitserk jumped ship. But it may not be true, it’s just the reasoning they come to because they little else make sense of this close relationship.

This relationship continues well into Season 6 and there is a resolution — you discover in time why he jumped ship. But there are many feats to come. In the meantime, it’s the voyage to discovery for both of them that they love and hate each other. They’re bound together by some forces that they don’t understand. Just like when Hvitserk was a young kid he was also protective towards Ivar, so he’s horrified by some of the things Ivar does. But he also understands where Ivar has come from and the tribulations he has gone through and the fact that he’s a cripple. As far as he can he continues to try and protect Ivar throughout almost whatever Ivar does, despite being shocked and appalled by them. But Ivar exerts and almost mesmeric power over people around him. Over Hvitserk and in some ways over the audiences. You want to dislike Ivar because of the things he does but you can’t quite dislike him. Part of you admires some of the things he does even because he is a cripple and it’s been very, very hard for him to grow up in a Viking world. That relationship is absolutely central to the story now and going forward.

“Vikings” airs Wednesdays at 9 p.m. on History.

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