'Vikings' season 4 spoilers, plot news: 4 cast revealed; comic book version of Lagertha's journey to be released

The recent buzz among "Vikings" fans is about the four new actors who will be joining the second half of the fourth season.

"Vikings" season 4b will return after a six-year time jump following the events of the midseason finale. At that time, Ragnar's four sons will have grown up. The siblings will become adult Vikings anxious to prove themselves and ready to vie for Kattegat's kingship.

The sons, Hvitserk, Ivar, Ubbe, and Sigurd, will be portrayed by actors Marco Islo, Alex Hogh Andersen, Jordan Patrick Smith, and David Lindstron, respectively. Their casting was a well-kept secret for some months, with the young men not being able to share the news with family or friends.

Smith pointed out, regarding their roles, "It's almost a new generation to Vikings. Vikings, staying true to the era, is young men becoming warriors ... You need other people to come in to keep the fighting and the life of Vikings alive..."

Ragnar's sons grew up without their father looking on, and so, they will be caught between their interest in what has become of him and resentment for his disappearance from their lives.

Smith's Ubbe became the father figure then, looking out for his younger brothers. Islo described Hvitserk as the silent type and a "relaxed warrior. According to Lindstron, Sigurd grew up as the "teen rebel," sensitive and emotional, but with a "strong sense of right and wrong." He also harbors a grudge against the youngest brother.

Smith, Islo, and Lindstron agree on one thing: Andersen's Ivar will be the fan favorite.

Ivar is said to be the "most Viking" of them all "because of his entire life as a cripple in an environment that does not embrace it, he's the toughest one of them all," as Ragnar realized. In fact, Ivar will later become the great Ivar the Boneless, who will later take over the world.

Their appearance on the show at this time will spark a lively interest from the audience and invigorate the "Vikings" season 4b when it returns later in the year.

In other related news, a comic book version featuring Lagertha's (Ragnar's former wife) journey from Paris will outline the aftermath of the events at the midseason finale. She is imperiled and will need to fight her way home. Titan Comics will be launching the miniseries in September.