It is the age of Ragnorok. The daily drudgery of conquest, pillage and rape is getting Erik down, and after accidentally killing a woman he tries to defend, he seeks enlightenment from a cave - dwelling seer.
This is the Dark age, she tells him, which will end in an orgy of fighting and destructiveness.
Determined to do something about it, he sets out with a long-ship full of squabbling warriors to awaken the gods with the Horn Resounding so that they may usher in the new era of peace and light... Simple really!