The first DLC for XCOM: Enemy Unknown is called called Slingshot and will include a new single-player campaign, according to a press release from developer Firaxis.
Slingshot is first of two planned DLC pieces and will include three new Council missions, three new maps, and its own story arc, featuring "a badass Triad operative named Zhang," designer Ananda Gupta told Joystiq. Gupta said that the DLC will include more varied objectives with new mechanics.
Players will have to start a new game to access the content, though the game allows players to begin the missions whenever they choose. The DLC also allows players to unlock the Blaster Launcher, a weapon that was previously only available late during the campaign.