Strong brutal violence.
The main theme of the movie is that vikings have come to slaughter native americans and the man that ends up saving the natives is in fact the son of a viking so the vikings are coming after him and the natives.
Nonstop graphic violence including throat-cutting and beheadings all shown onscreen with blood flowing from the wounds.
In the beginning of the film Sunfire goes into a cave, and 100s of dead corpses are shown graphically...then a flashback is shown with savage vikings murdering the natives in cold blood.