'Vikings' season 4 episode 18 spoilers: The legendary Great Heathen Army brings vengeful war to Northumbria in 'Revenge'

The Great Heathen Army has begun to come together, and Ragnar's vision of a vengeful war is about to come to life in the next episode of "Vikings."

Simply titled "Revenge," the next episode of History's take on the Viking lore will finally bring Ragnar's plan to fruition as the great Viking army led by his vengeful sons make it to the coast of Northumbria. But is this really all the revenge that will be featured, or will the one that Ivar (Alex Høgh) wants to take on Lagertha (Katheryn Winnick) also come to pass in an unexpected way? And with the Queen's son, Bjorn (Alexander Ludwig), back from the Mediterranean, will a bloody battle among brothers ensue before the army sails off to do Ragnar's bidding?

The trailer for the next episode shows the infamous Great Heathen Army going to war against King Aelle (Ivan Kaye) of Northumbria. But does being the largest Viking army in history ensure their success, or will some form of Divine Intervention bring Ragnar's proud sons to their knees?

One other issue that's been left hanging since it was hinted at is Lagertha's (Katheryn Winnick) fate in the hands of Ragnar's sons. While Ivar seems to have the deepest bloodthirsty grudge on her for killing their mother, Lagertha seems to regard Ragnar and Aslaug's (Alyssa Sutherland) eldest son, Ubbe (Jordan Patrick Smith), as someone she can reach out to and reason with.

In an interview with Entertainment Weekly following the previous episode, series creator Michael Hirst shared that all of Ragnar's sons have each inherited different aspects of him, but Ubbe is the closest to his father psychologically.

"It was in my mind that Ubbe was the inheritor of Ragnar's philosophy, and in strong ways, his temperament," Hirst said.

Lagertha has always been aware of the danger that Ragnar's sons impose after Aslaug's death, and when she commented that Ubbe resembled his father in Ragnar's earlier years, it was at its very core a silent plea for her life.

"She's hoping, perhaps, that he's not going to be like Ivar and insist on her death," Hirst added.

"Vikings" season 4 episode 18 airs on Wednesday, Jan. 18, at 9 p.m. ET on History.