The lovely chaps over at Robot Entertainment have announced a release date for the upcoming "Lost Adventures" DLC for https://www.trueachievements.com/Orcs-Must-Die-xbox-360.htm
The upcoming DLC will be available to download on December 14th for a mere 400 MSP. A slice of info on the "Lost Adventures" was included with the announcement of the release date via Robot Entertainment's Blog
Return to the dead world beyond the rifts and conquer a new series of five challenging fortresses. In Lost Adventures you’ll travel from the depths of the Pit to the narrow passages high over the Great Gorge. The Lost Adventures are five of the most deadly rift assaults the War Mage has ever faced. In addition to the new fortresses, you can expand your War Mage’s arsenal with two new traps and three new defenses. You’ll be demolishing levels, beating your friends on the leaderboards, and most importantly, killing a bunch of orcs deader than dead.
More details on the "Lost Adventures" DLC, covering information on new fortresses, enemies and additions to the War Mage's toolbox along with a couple of trailers, can be found here