Vikings: Everything to Know About Season 5

When Vikings returns for its fifth season, it's going to be brother against brother in a bloody civil war.

Although Ragnar's (Travis Fimmel) sons joined together to avenge their father's death, it won't take long before the cracks in their union begin to spread -- something only exacerbated by Sigurd's (David Lindström) death at the hands of Ivar (Alex Høgh Andersen) in the Season 4 finale. But according to creator Michael Hirst, even if Ivar hadn't killed Sigurd, the brothers would have turned on each other eventually.

"You might say that it's almost inevitable that the brothers are going to turn on each other because that is something that, in powerful families or families where there's questions about a lot of money or a lot of power, it's the siblings who tend to turn on each other," Hirst tells TV Guide.

As Ivar, Bjorn (Alexander Ludwig), Ubbe (Jordan Patrick Smith) and Hvitserk (Marco Ilsø) each choose a side this season, they will find themselves forced to make tough decisions that reveal where their true priorities lie: in protecting Ragnar's legacy or attempting to secure their own.

Vikings Mega Buzz: Lagertha Knows Her Days Are Numbered

So who will threaten their father's work? And how will this civil war affect the rest of our favorite heroes (and villains)? Check out our full rundown of what to expect of Vikings Season 5 below.

Lagertha's (Katheryn Winnick) rule will be questioned.

The current ruler of Kattegatt, Lagertha finds her reign questioned at every turn this season. Unlike her (male) predecessors, who addressed issues with quickly dispensed violence, Lagertha prefers to search for alternative solutions, which doesn't always work in her favor.

"She's going to lose some support because people think of her attitude, perhaps, as a weakness. If you just go out and slaughter everyone who's in your way, that may be seen as a strength, but it's also sometimes stupid, and I don't think it's a weakness [to not do that]," Hirst says. "I think that she's a very, very strong individual, but she makes decisions and some of them are going to go wrong, which is what happens."

Ivar will find great power, but no true allies.

Although Ivar does have a deep regret over murdering his brother, don't expect him to get all touchy-feely all of the sudden, or even to show any remorse at having to turn against his own family in his quest to avenge his mother.

"As I say, he doesn't necessarily need friendship. He needs allies," Hirst says of Ivar's perspective this season. "He's very dangerous to all his brothers, to everyone."

Vikings Star Says Ivar Will Try to Avoid War with Bjorn (at Least at First)

With the Great Army behind him, Ivar will make a powerful foe to Lagertha and he will stop at nothing this season to seize control of Kattegatt, even at the risk of destroying everything Ragnar worked so hard for. But while Ivar will amass a great force of allies, it remains unclear whether he has what it takes to keep them loyal in the long run. It'd be a real shame if Ivar were to win the battle, only to lose his spoils to another usurper.

Ubbe will face a tough choice.

Ubbe finds himself in a very complicated position this season, torn between turning against his brothers to defend his father's legacy and aligning himself with the woman who killed his mother. Ubbe will (at least temporarily) decide to work alongside Lagertha to support her claim to Kattegatt in the first half of this season, but his contradictory feelings on the issue won't be resolved anytime soon. "I'm writing the sixth season now and some of these issues are still live issues," Hirst reveals.

Ultimately, what drives Ubbe's decisions are his own ambitions and agendas, which are the closest aligned with Ragnar's own dreams. "The thing about Ubbe is that he's the son who is, in many ways, the most like his father. He really believes in Ragnar's philosophy of finding farmland," Hirst says. "He's the most sensitive one. He tries to navigate through all these terrible brotherly conflicts and stuff and we'll see how far that gets him."

Bjorn will seek out his own destiny.

Once again, Bjorn will venture to the Mediterranean this season. Only unlike his last trip, viewers will get to see quite a lot more of Bjorn's journey abroad, which will make for a stark contrast to what fans are used to seeing in this series.

"I think a lot of people when they see Bjorn on a camel in the Sahara Desert will go, 'what the hell? I mean, this can't be, right?' But I can assure you that it's absolutely historically accurate, which is weird," admits Hirst.

Exclusive Vikings Sneak Peek: Will Ivar's Brothers Forgive Him for Killing Sigurd?

However exciting Bjorn's journey may be, it also will be far from a success, so it isn't long before he's back on the sea, heading home to Kattegatt where he will help Ubbe and Lagertha figure out their best chance at defeating Ivar and the Great Army.

Hvitserk will make a shocking decision.

After Ivar seizes control of the Great Army, the alliances between all of the brothers begin to shift. But while most of the brothers' allegiances are easily predictable, Hvitserk makes the shocking choice to go against Ubbe and align himself with Ivar.

Vikings Mega Buzz: "All Bets Are Off" For Rollo's Explosive Return

"That's a big moment," Hirst says. "I think even Hvitserk isn't sure why he's done it, but Vikings are always dealing in fate. 'What is my fate? What am I fated to do? Who should I be with that justifies my fate?' So the answer to your question is very complicated, but Ivar is a force of nature."

Following that life-changing decision, Hvitserk won't feel 100-percent confident with his choice, particularly since his show of loyalty to Ivar won't earn him much trust from the Great Army's leader.

Floki (Gustaf Skarsgard) finds a new purpose.

After the deaths of his best friend, wife and daughter, Floki will have lost his patience for the mortal world, and so he sets off from Kattegatt with no destination in mind, nor any supplies to sustain him. After fully submitting himself to the wills of the gods, Floki will find himself in Iceland, which he believes to be the land of the gods and the source of his new purpose: to build a world for the true believers.

"Now whether this is in his head or not is something we'll find out in due course because, of course, when he leaves in his open boat, it's perfectly possible to think he's crazy. That may be one interpretation of his actions," Hirst teases.

But whether or not the gods were at work in Floki's new adventure, the gods' influence on Vikings can't be denied, according to Hirst. As the creator recalls, he chose to call Skargsard's character Floki because of its similarity to the name of the Norse god Loki. But when he decided Floki would land in Iceland in Season 5, Hirst began researching who actually was the first to discover the country. "I discovered, much to my surprise, that the Viking who discovered Iceland was called Floki," Hirst explains. "So this means that it's not really me writing the scripts, it's the gods."

Heahmund (Jonathan Rhys Meyers) will make quite the impression.

Fans got their first glimpse of Bishop Heahmund in the Season 4 finale, but that was just an amuse-bouche compared to the meal Jonathan Rhys Meyers serves this season. This warrior bishop with an insatiable lust for women is exactly the type of complex character that Vikings thrives on, and Heahmund quickly asserts himself as one of the series' most fascinating faces.

Vikings Renewed for Season 6 Ahead of Season 5 Premiere

A skilled warrior fighting ruthlessly for what he believes, Ivar recognizes a kindred spirit in Heahmund instantly when the pair first meet on the battlefield. But as Heahmund begins spending more time with the Vikings (not exactly by choice, mind you), it isn't Ivar who Heahmund grows to admire and respect. In fact, Heahmund will grow to admire one Viking in particular, which will only further complicate his already murky moral conundrums.

Harald (Peter Franzén) will take a stand.

This season, Harald will help fill the void King Ecbert's (Linus Roache) death created, as the ambitious Viking takes his biggest steps yet towards achieving his dreams of becoming King of Norway. "He's absolutely determined and ruthless," Hirst says of Harald this season.

But there is one thing that threatens Harald's take-no-prisoners attitude: the fact that his brother Halfdan (Jasper Pääkkönen) has pledged himself to Bjorn. Harald will struggle with his brother siding with the heir to the kingdom that he hopes to conquer, but don't expect this quandary to slow him down too much.

"He will always be in the picture as long as he's alive," Hirst teases. "I can't tell you when he won't be alive, but as long as he's alive, he'll always be conspiring. And it may or may not come true that he realizes his ambition, but if anyone in that world can achieve his ambition, then it's Harald."

Rollo (Clive Standen) will return a changed man.

The last we saw Rollo, he had returned to his wife in Normandy and officially left his Viking life behind. But as we previously reported, we haven't seen the last of the conflicted warrior. Rollo will return this season -- although we won't tell you when -- but he'll be far from the Viking fighter we used to know.

"He is a different person when he comes back," Hirst says of Rollo truly embracing his new role as the Duke of Normandy. "It's a fabulous success story for him, but he does come back as a changed person, a different person." One thing that defines Rollo's new status: power, the kind that will result in some truly surprising turns of events for both his surviving family members and viewers.

Vikings returns Wednesday at 9/8c on History.