IGN writes: "We get down and dirty with the sadistic Dark Eldar. THQ sent over a demo, one that will be released soon to the public (rumor is January 15th), which we played to get a feel for the Dark Eldar faction. The demo only allows access to this faction against the Space Marines over two maps: a skirmish and one of the campaign stronghold missions.
The Dark Eldar are really like an angry version of the regular Eldar that like to torture and enslave other races. In fact, their builder unit is called the Tortured Slave and looks like a terrified and unhappy human. Since the Dark Eldar society is largely based around slave labor, their population cap is increased by warping in slave pits. These also can be upgraded to provide an endless supply of dead bodies (which can have their souls harvested) or acquire an ability to seriously damage the morale of enemies in the area."