Vikings' final season is underway, which means nothing is off the table anymore. Anyone can die and anything can happen — well, not anything, according to star Alexander Ludwig, who plays Bjorn. When the actor stopped by our studio recently, we asked him to weigh in on five of the craziest Vikings fan theories currently still in play, and while he didn't hesitate to shoot some of them down, he did give hope that a few might actually be credible. Check out Ludwig's reactions to the biggest Vikings fan theories below and in the video above.

1. Hvitserk is the true mastermind. Hvitserk's (Marco Ilsø) motivations are so murky that some fans are thinking this whole existential crisis is nothing but one big ruse. The theory posits that Hvitserk is orchestrating events so that his brothers turn against each other and take each other out so that he can easily rise to power and claim the crown. Ludwig called this theory "amazing," but added that he can't really see it happening, unfortunately.

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2. Floki is actually the god Loki. There is a lot of mystery this season about what happened to Floki (Gustaf Skarsgard) in Iceland, but the real mystery surrounding Floki isn't about his death but about his potential origins. Since the show's inception, fans have speculated that Floki is an incarnation of the god of mischief, Loki, and Ludwig is right there with them. "I believe so," Ludwig said when asked if Floki could truly be a god. The actor noted that whether or not this is the case will likely be "left up in the air," but that the Season 4 episode "Yol" featured a potentially massive hint that this theory is true.

"If there's any specific scene that would hint to that, it would be when the Seer licks Floki's hand, as opposed to the other way around, which is what we've seen up until then," Ludwig explained. "For any fervent Vikings fans, that would mean a lot to them, I think, if they were reading into it."

3. Rollo is also Ivar's father. Last season, Vikings confirmed the major fan theory that Bjorn potentially isn't actually Ragnar's (Travis Fimmel) biological son, but Rollo's (Clive Standen). And some fans think Rollo might have sired another one of the brothers, Ivar (Alex Høgh). However, simply the fact that the two share similarly dark hair isn't enough to get Ludwig on board with this one. "I don't see it. Maybe," Ludwig said with a laugh

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4. Sigurd will be the son to kill Lagertha. This is definitely the most out-there theory of them all and posits that Sigurd (David Lindstöm) wasn't actually killed by Ivar and has merely been in a coma this entire time. According to this theory, Sigurd will wake from his coma at some point in this final season and kill Lagertha (Katheryn Winnick), fulfilling her destiny to die at the hand of one of Ragnar's sons. So, uh, what does Ludwig think of this totally reasonable and not insane theory? "That's for sure happening," Ludwig joked.

5. Ragnar is still alive. Yes, this is yet another theory that a character we saw die onscreen is actually still kicking it somewhere. One explanation for how it could be possible is that Ragnar had made himself immune from snake venom prior to being dropped in the pit, which — if we're being honest — does not sound feasible at all. But the show did fake Ragnar's death once before, so fool me once, etc. etc.

As for Ludwig's thoughts on the matter, he noted that he hopes "[Fimmel's] character does return in some aspects" but that Ragnar has already lived on through his sons. "One thing Travis and I worked extensively on was that Bjorn would emulate certain mannerisms that his father had to show that 'like father, like son.' So for me that was a really exciting challenge, was being able to still have Bjorn as his own man, his own identity, yet still show aspects of his father shine through. And I think through all the actors and all the brothers, we've all kind of tried to show not too much but little hints to that. So in a way, he's never really gone."

Vikings airs Wednesdays at 10/9c on History.

Additional reporting by Kelsey Pfeifer

(Disclosure: TV Guide is owned by CBS Interactive, a division of ViacomCBS.)