Besieger is a real-time strategy game where it is up to the player to find Thor's hammer and set things straight again as the vikings, fight as the Cimmerians or play as the returning Korin in three different single player campaigns.

When Korin, rightful king of the Cimmerians sets on a quest to find a fabled magic sword, his sister Mara sees her chance and seizes power with her dark magic. Vikings that live nearby hear of this and fear an attack. Therefore they send out some warriors on a quest to find Thor's hammer. They set out on a flying ship, only to be shot down and see Mara's forces destroy their capital.