"This is not a prequel and this is not a follow-on chapter that extends the story," designer Ananda Gupta told GameSpot. "Instead, [it's] the same alien invasion that you confronted in XCOM: Enemy Unknown, but with a lot of new stuff added."

Included with Enemy Within are new soldier abilities like Gene Mods, which allow players to construct a Genetics Lab to enhance players abilities, including augmentations to their characters' chests, brains, eyes, skin, and legs.

Enemy Within also introduces a new Trooper Class called MEC, short for Mechanized Exoskeletal Cybersuit. This class has specialized abilities and every suit can be upgraded with new weapons like the flamethrower and grenade launcher.

The expansion also brings eight new maps to Enemy Unknown--bringing the game's total to 13-- as well as new weapons, equipment, and "lots" of new enemy types like the Mechtoid.

A new feature called Offline Squad Editing will also be introduced in XCOM: Enemy Within. This much requested feature, according to Gupta, will allow players to select multiple configurations of squads offline, while they are under no time pressure.

On top of that, Enemy Within packs in a new strategic resource called Meld, which works differently than other resources in the game.

"The way Meld works is it shows up in these canisters that are on the battlefield," Gupta said. "And the Meld canisters all have self-destruct timers. So players who have become accustomed to a very conservative play style, where they only use the best cover and they#163;take their time, they're very meticulous about their soldier moves#163;.you can still do that, but you won't get as much Meld."

These Meld canisters will also be added to Enemy Unknown's original five maps to bolster replayability, Gupta said.

Lastly, Enemy Within will add all localized languages to the game's character customization options. Players will be able to assign a different language to every character, in any combination they want, choosing from English, French, Italian, German, Spanish, Russian, or Polish.

"We really wanted to improve the international feel of the squad, and we feel like this is the best way to do that."

Enemy Within will launch November 12 for Xbox 360, PlayStation 3, and PC/Mac. On PC/Mac, the content will cost $30 and will be available as a traditional downloadable expansion to Enemy Within.

On consoles, Enemy Within can be purchased for $40 as a standalone download in the form of the Commander Edition. In addition to the new content, this bundle features previously released DLC like the Slingshot expansion and Elite Soldier Pack.