This is History Channel's Vikings (WIP) for the game.

History Channel's Vikings (WIP) is an add-on for the game that allows you to play as Ragnar in the Viking age. You can fight in battles and go on raids, like the ones you saw in the movie. The mod is based on the historical figures of the Vikings and lets you play as them. It is made for the sandbox game and will change your character to Ragnar and let you play with all of your friends from your campaign.

It is recommended to use it in a new sandbox campaign, and you can also try to play a sandbox game with your friends.