If you thought Athelstan's (George Blagden) death was bad, you better prepare yourself for Vikings' fourth season. According to creator Michael Hirst, there will be even more painful demises ahead when the History drama returns.

"Personally, I think this is our best season," Hirst tells TVGuide.com. "And yes, there are some devastating moments that were - as usual for me - quite difficult to write and to say goodbye to people. We do death very well I think in Vikings, but it's a hard road."

Check out what else to expect from Vikings super-sized fourth season, which will air 10 episodes this spring and another 10 episodes later this year.

This season, Ragnar (Travis Fimmel) is really struggling with his own purpose and why he is still alive. How will that affect his relationships and the way he rules?
Michael Hirst:
I think that Ragnar finds it increasingly difficult to carry the burden of kingship. ... I think that getting into Paris almost killed him and he was rather looking forward to being in Valhalla, in one way, but it's denied him and he has to pick up the burden again. And a lot of the new season is about how he deals with the burden and, of course, the particular focus he has on the relationship with his brother. The Vikings are going to go back to Paris, obviously, because historically speaking, if the real Vikings found a place that was great to plunder and full of possibilities and riches, they would go back year after year. But it's not in Ragnar's nature to go back to somewhere just to plunder. He's not interested in that side of things. So for him it becomes personal - the final confrontation with Rollo (Clive Standen).

Aslaug (Alyssa Sutherland) seems to have lost her affection and respect for Ragnar. How can we expect that relationship to play out?
Hirst:
It's been a difficult marriage. As all the fans of the show know, Aslaug's appearance disrupted what had looked like and what was a very, very deep and long-standing love between Ragnar and Lagertha (Katheryn Winnick). I always say that I'm kind of with the fans who want them to get back together, and it's always a grief to me that I'm not putting them back together. ... But there are no bells and roses ahead for Aslaug and Ragnar, and it's going to be a very difficult and dark journey. Not least of all because Harbard (Kevin Durand) is going to return and stir up a lot of feelings that she's been repressing, and it's going to be very, very difficult for her.

Vikings exclusive: See Rollo's disastrous wedding night!

Bjorn (Alexander Ludwig) is determined to prove himself as his own man this season. How will we see him attempt to step out of his father's shadow?
Hirst:
I feel for Bjorn. I feel that, like a lot of kids today, he comes out of a broken marriage and his parents are both strong individuals. He's found it tough to establish his own identity and I think that's a very common thing today. I totally understand that he wanted to go away and find himself and put himself to the test. As he says to Ragnar, "I'm going into the interior, I'm going into the wilderness, I'm going into the ice field, because you don't think I can survive." So he's testing himself.

Rollo has now forsaken his own people to live in a society where he doesn't even speak the language. What does his assimilation process look like?
Hirst:
There's a certain comedic aspect to it, because a lot of the Franks regard him as little better than a beast of the field, like a kind of ignorant, savage man - especially his new wife. But the pathos of it is that he believes very strongly that this is what the gods intended for him. So he's turned against his own people because he genuinely thinks the gods had this in mind for him. So he has to live through the humiliations, live through being patronized by the Frankish elite, to find his destiny. This is a season about Rollo really discovering what his own destiny was from clues and half-hints from the Seer. So he's on this journey, which involves him betraying his brother yet again, in order to find himself.

Floki (Gustaf Skarsgard) was one of Ragnar's closest friends, but then he killed Athelstan. What type of repercussions can we expect from that? And is there any room for forgiveness in that relationship?
Hirst:
Of course that's a huge issue for Ragnar. We know what Athelstan meant to him, and it puts an incredible, almost impossible strain, on his old relationship with Floki. But it's still something that Ragnar has to work through. He knows in a way that he ought to kill Floki for the betrayal. He finds it incredibly difficult to do so. He's looking for a way out. He can't think of a way out himself, because he knows what he ought to do and it's another burden of power. It would need some deus ex machina. It would need some other unexpected force or intervention that would allow him to release and forgive Floki. So the only way that Floki can survive this situation is some unexpected and outside intervention into the situation.

Vikings returns Thursday at 10/9c on History.