Stefan, the last scion the deposed ruling family of Ostermark, his father and grandfather executed for Chaos Worship and his own face branded with the titular Mark of Chaos leads the armies of Ostermark in a desperate bid to beat back the Northmen Hordes encroaching the Empire at the behest of the Count Otto Von Gruber. But he soon finds not that all is as it seems in the Empire.
Thorgar the Blooded One, a powerful Norse warrior and champion of the mighty Chaos Gods is visited by a herald of the Gods who tells him that his dread deities have set their gaze upon him and have chosen him to take up the mantle of the fallen Asavar Kul. Thorgar must unite the clans and warbands of the North into a mighty host that shall sweep aside his foes and ultimately bring about the End Times.
The expansion pack, Battle March, deals with the aftermath of the invasion of Thorgar (and it's not quite made clear who won) and the encroaching Greenskins who seek to take the scraps of what is left. Led by the brutal Warboss Gorebash and his shaman adviser Wazog; the Orcs and Goblins spill down from the mountains in a mighty WAAAGH! following a set of arcane signs leading them to battle, each leading to one more perilous than the last. Concurrently, the Dark Elves of Naggaroth use the chaos to launch their newest attack against their High Elven cousins of Ulthuan. But both factions are more entwined than they appear at first glance.