Warhammer 40K: Dark Millennium Online was a large scale war and combat-focused MMORPG from Vigil Games and THQ. The game was set in the 41st Millennium, well after the events of the Horus Heresy, somewhere in the Sargos Sector. The Sentinel Devices that helped prevent the ferocious Warp Storm from unraveling the fabric of reality were weakening. The forces of Order and Chaos were arriving in the sector to either investigate and repair the problem, or take advantage of the situation in order to help speed up the process.
In true Warhammer 40K fashion, war between Chaos and Order were the focus of gameplay. The game was to feature an in-depth combat system that allowed players to form up together as squads and make intelligent use of cover, suppressive fire and flanking. Very little detail was released about classes, only to say that there were to be no non-combat classes.