So to catch up, here's what the press release says about "The Last Stand"
The Last Stand is a cooperative survival mode that gives gamers control of an individual hero unit and drops a small multiplayer team into a battle with impossible odds. Players can choose between a Space Marine Captain, Eldar Farseer or Ork Mekboy and will team up with two other squad-mates in an attempt to hold out as long as possible against wave after wave of relentless attackers. Hero units level up and are fully customizable as new armor and weapons become available from game to game. Working together to devise innovative strategies is the key to success in this brand-new battle mode.
The Last Stand download also contains two new multiplayer maps, balance updates and bug fixes for Warhammer 40,000: Dawn of War II.
With the pending release Relic has announced a contest, details and the trailer for "The Last Stand" after the jump.
The contest involves trying to survive to the 20th wave, and taking a screenshot. Winners will get some cool Dawn of War II swag including a Chaos Marine miniature.
All the details are at the link above that I'll relink now.
And the trailer for "The Last Stand"