Vikings: The One Relationship That's Most Important to Ragnar 

Vikings: Ragnar and Ivar\'s Relationship Is Incredibly Important

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Full spoilers for Vikings\' Season 4b premiere, "The Outsider," continue below.

Ragnar and Ivar are off for the father/son bonding trip of a lifetime, but it\'s a journey that\'s already had its share of ups and downs.

The Vikings: Season 4b premiere focused largely on Ragnar trying to recruit as many of his former allies as he could on his quest to confront King Ecbert. Though he ended up leaving Kattegat with just Ivar by his side, star Travis Fimmel thinks everything worked out the way Ragnar wanted.

"His relationship with Ivar I think it\'s his favorite relationship," Fimmel told IGN on a visit to Vikings\' set. "It\'s a bit like that Johnny Cash song \'A Boy Named Sue\' where the father did a lot of stuff because he knew he wasn\'t always going to be there for him, to really toughen him up and just to show him that his weakness is actually his strength. ... Ragnar sees a mind in Ivar that nobody else sees and doesn\'t treat him as a cripple -- admits he\'s a cripple, but he always believes that his mentality is the strongest thing."

The premiere saw Ragnar going to each of his closest friends after an extended absence and asking them to uproot themselves to come on a mission with him. While these are people who would have jumped at the chance in previous years, by now their relationships with Ragnar have frayed. That doesn\'t stop them from feeling a bit conflicted about turning down Ragnar for his big adventure.

"[Bjorn] knows that he might never see it again," said Alexander Ludwig. "I think that there\'s this immense guilt. You never know what\'s going to happen when you go on this immense voyage, whether or not you\'ll come back. ... He had a choice and he made his choice. He knows his father would have made it [too]."

Lagertha has all but left her relationships with men behind, finding a new romance with the shieldmaiden-in-training Astrid. Though she\'s moved past her romantic feelings for Ragnar, Kathryn Winnick thinks he\'ll always have an important place in her heart

"To sum it up, I would say that it\'s complicated between Ragnar and Lagertha. He has changed. He\'s not the man she originally fell in love with, but she knows him better than anyone else so I think there\'s a true love there, like you would love your very first boyfriend," she said. "She feels that Ragnar\'s choices, even though he made bad choices, he didn\'t fulfill them or he didn\'t necessarily execute his plans right and his weaknesses as a human being got in the way of his strength as a ruler. I think that sums it up, the fact that he let his ego and dark demons, if it was taking mushrooms or taking wrong choices to fight against Rollo his brother and not making the right choices for the people. I think Lagertha has been around that, has seen that, won\'t ever forget it, and I think that\'s why she wants to be queen of Kattegat and also do what\'s right for her people."

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Even though Floki turned down Ragnar\'s offer, he got the interaction he\'s always wanted with his longtime friend: an acknowledgment of Ragnar\'s feelings toward him.

"In one way, that\'s everything he\'s ever asked for is Ragnar\'s love and confirmation and validation. He hasn\'t had it in so long, and then he finally says, \'I love you,\' and [Floki] does," said Gustaf Skarsgard. "It completes Floki in a way. He does [find peace]. I\'m not saying it\'s going to be an ever-lasting peace -- he\'s still driven by his own biochemical disruptions in his brain. I don\'t think he\'s going to be remain peaceful forever, but he\'s definitely come to peace now and matured as well."

For now, that puts a period at the end of most of Ragnar\'s primary relationships, and allows him to focus on developing Ivar into a leader. "He just wants to talk with Ecbert," said Fimmel. "He\'s just going to talk and to teach his son Ivar what it\'s all about. He believes Ivar is going to be the best leader out of anyone."

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According to Alex Høgh Andersen, this father/son bonding time couldn\'t come at a better time for Ivar -- and based on the way things panned out in the premiere, Ragnar will hopefully straighten his son out.

"The thing about Ragnar and Ivar is Ivar really needs him. He\'s in a place right now in his life where he needs something new," said Andersen. "He\'s in his late teens and he\'s been having a very tough, horrible life so far, never been a part of the family, never been a part of the brothers, always been watching everything from a distance. In those late teens, you need to get something going. You need to get some ambitions. You need to develop, and Ragnar gives him that opportunity."

Terri Schwartz is Entertainment Editor at IGN. Talk to her on Twitter at @Terri_Schwartz.