The game was released for Microsoft Windows in the US on November 14, 2006, with subsequent release in PAL territories on November 23, 2006. It saw a digital re-release as Warhammer: Mark of Chaos - Gold Edition on March 9, 2020, via the digital distribution site GOG.com.
Stefan von Kessel, 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, as the high elf mage Aurelion soon arrives with portents of a great threat that could spell doom for them all.
Thorgar the Blooded One, a powerful Norse warrior and champion of the mighty Chaos Gods is visited by a herald of the Gods, Sudobaal, 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. To aid him in this most unholy endeavour, he recruits all manners of marauders and monsters to his side, including a force of Skaven led by the wily Kasqit.
Battle MarchThe expansion pack, Battle March, deals with the aftermath of the invasion of Thorgar and the encroaching Greenskins who seek to take the scraps of what is left. Led by the brutal Warboss Gorbash 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, led by Lilaeth and Kaeleth, use the chaos to launch their newest attack against their High Elf cousins of Ulthuan. But both factions are more entwined than they appear at first glance.
- The Empire campaign sees Stefan and Aurelion defeating Thorgar the Blooded One and successfully defending the city of Talabheim from a Chaos invasion, whereas in the Chaos campaign Thorgar and Kasqit work together until Thorgar eventually ascends to become a Daemon Prince and razes Talabheim.
- Thorgar the Blooded One can choose either Nurgle or Khorne as his patron in his quest to ascend to daemonhood. Whichever god he does not choose will instead support Sudobaal as the treacherous sorcerer tries to overthrow Thorgar. In the Empire campaign Thorgar defaults to a Khorne Daemon Prince in the final mission.
- The Battle March expansion does not outright state whether it was the Empire or the forces of Chaos that triumphed in the original game. However, in Battle March Aurelion was still alive whereas in Thorgar's original campaign she is killed, which would seem to indicate that Stefan Von Kessel and Aurelion were the true victors of the conflict and that the city of Talabheim subsequently did not get razed.