King Ragnar Lothbrok died in Vikings season 4 but his legacy lives on through his sons Bjorn and Ivar the Boneless. The duo has formed a great army to defeat King Ecbert and Prince Aethelwulf.

The finale of History Channel's periodical drama is titled The Reckoning and the synopsis suggests that there is an evil war plan cooked by Ecbert that will be the decider in the epic battle. Click here to watch the episode via live stream online.

While the Lothbrok sons were busy attacking Aethelwulf and his army with their vicious Vikings war tactics, the ruthless king of Wessex has a backup plan that no one is aware of. The sons of Ragnar will have their reckoning with the army of Wessex.

In the promo for episode 20, Floki, Ivar and Bjorn enter a gated territory only to find it deserted with movements beyond the wall. It remains to be seen what result the war will yield and how it will set the stage for season 5 in episode 20, which will introduce a new character on the show played by Jonathan Rhys Meyers.

The official synopsis for the episode reads: Prince Aethelwulf finds himself subject to the Vikings' battle master plan; Ecbert remains behind with a plan of his own.

Show creator Michael Hirst talked about the new character of the warrior bishops Heahmund. "I was looking at the history books, and I came across these warrior bishops," he told Entertainment Weekly. "The antecedents of the Knights Templar: these are people who were absolutely religious, yet they put on armor and they fought. Don't let their priestly status fool you, either. "They were crazy! They believed totally in Christianity and the message, and yet, on the battlefield, they were totally berserk."

Hirst promises that Heahmund will be the perfect nemesis to Ivar in the upcoming season. He said: "He's a man of Wessex, and he's gonna come in as a worthy opponent to Ivar. His whole life is about deeply passionate commitments. He's a wild card who happens to be [played by] Jonathan Rhys Meyers, who is himself kind of a wild card!"

Vikings season 4 airs every Wednesday on History Channel.