Space Marine puts players into the role of one of humanity’s elite soldiers, as they battle to protect an Imperial Forge World from a millions-strong Ork invasion. But this isn’t all that faces Captain Titus of the Ultramarines. When Titus makes planet-fall, he soon realizes that the forces of Chaos are lurking in the shadows pulling the strings for their own nefarious purposes.

The addition of Chaos forces adds more variety to the Space Marine single-player campaign by complementing the animalistic and horde-like Orks with a much more powerful and strategic enemy. While Titus can dispatch dozens of Orks alone, the Chaos Space Marines are more than capable of going toe-to-toe with him, especially with the support of Renegade Militia, Tainted Psykers and Bloodletter Daemons, among other units.