Kattegat has a new set of Viking warriors when "Vikings" returns for the second half of season 4.

Ragnar (Travis Fimmel) and Rollo's (Clive Standen) highly anticipated face-off finally happened in the midseason finale of "Vikings" season 4, but neither of them was killed. The episode concluded with a big time jump, leading to the midseason premiere where Ragnar's little sons finally grew up to become fine young Vikings.

After Ragnar's defeat to his brother in Paris, the King of Kattegat suddenly disappeared without a trace. The episode jumped over a decade to show that Ragnar's sons with Aslaug (Alyssa Sutherland) are all grown up and are perturbed about their father's fate.

The grown up Hvitserk is being portrayed by Marco Islø, and the young crippled boy Ivar is played by Alex Høgh Andersen. Ragnar and Aslaug's eldest son Ubbe is played by Jordan Patrick Smith, while the rebellious Sigurd is played by David Lindstrom.

According to IGN, the casting of the four actors was kept a secret for months. Even their families and friends had no idea why they had been spending a lot of time in Dublin.

In the midseason finale, Ragnar's sons started to hate him after he decided to abandon them and Kattegat after his failed raid in Paris. Series creator Michael Hirst told Variety that Ragnar's disappearance had a huge impact on his sons.

"They don't know where he is and the sons are in a kind of vacuum because they don't know he's dead so no one can be king, so it creates an interesting dynamic," Hirst said.

But Ragnar chose to return, and the family and the kingdom that he abandoned had gone through a lot of changes when he decided to reappear.

When asked what fans should look forward to when "Vikings" returns for the second part of season 4, Hirst said, "You can't second-guess what's going to happen, but it's just so emotional and as I say, I'm prouder of where we're going with these episodes than anything that I've ever written. I want people to be there, because season 4 will be startling and extraordinary."