Factual error: The Vikings raided England in the 9th and 10th centuries. The first castles were not built until post 1066. The castle in the film has rounded towers, crenellations and machicolations, which would date it at approximately 1300. That would tend to suggest that these Vikings were 400 or 500 years old, or that they had access to a time machine.
Factual error: At the end, when Kirk Douglas throws his head back and screams: "ODIN!", you can see several mercury amalgam fillings in his teeth - not available under most 900AD health plans.
