'Vikings' season 4 spoilers, plot news: Lagertha's fate, Rollo returning and Ivar as the new king

The second half of "Vikings" season 4 will see new rulers rising to power, a possible betrayal and more plots of revenge. Show creator Michael Hirst was more than happy to discuss of all this after the unforgettable midseason finale.

Will Rollo crawl back to his brother Ragnar in "Vikings" season 4? Or will it be the other way around? | Facebook/Vikings

Ragnar (Travis Fimmel) will now be building up his son Ivar (Alex Hogh Andersen) as his successor. The "Vikings" season 4 promo shows Ragnar's determination to prepare him for the throne while Ivar appeared to struggle but is still single-minded.

Hirst explained to TV Guide that Ragnar sons are different from one another but Ivar is the "most striking." He elaborated, "Ivar the Boneless is probably the most famous of all Vikings. He's a cripple, and yet he becomes this dominant, extraordinary alpha-male."

During an interview with Entertainment Weekly, Hirst revealed that Ivar will actually be the character "to take the show forward."

The "Vikings" season 4 trailer also teased that there's still a chance for Rollo (Clive Standen), who earned his victory against his brother in the midseason finale, to reunite with who he has been recently considering as his enemies.

While this hinted that reconciliation between Rollo and his brother is on the horizon, he would not want to tamper with the "good place" and sturdy footing he gained after earning success over the Vikings.

As for those worried about Lagertha (Katheryn Winnick), Ragnar's first wife is that not going anywhere, despite her precarious situation in the "Vikings" season 4 midseason finale.

Hirst said that she can't and won't kill her off, at least not yet because Lagertha is "the soul" of "Vikings" and there's a lot more in store for Winnick's fearsome shieldmaiden.

When "Vikings" season 4 returns, Ragnar will also learn of the existence of his son with Kwenthrith (Amy Bailey). It remains to be seen how it will affect him, but Hirst emphasized that Ragnar will head to England not for this discovery but for a completely different reason.

The "Vikings" creator revealed that Ragnar will be back to meet King Ecbert (Linus Roache). In "Vikings" season 4, Hirst intends to further illustrate the connection and similarity of the two, which he described as something "that no one else on the show had."

"I wanted to see them together again, talking about important things," Hirst said.

"Vikings" season 4 has no return date yet but it is rumored to premiere this July.