XCOM: Enemy Within is an expansion pack for XCOM: Enemy Unknown, a turn-based tactical strategy game. The expansion adds the ability to gene mod soldiers to add to their powers as well as the ability to create MECs, powerful robotic soldiers. These new features are created by collecting a resource called Meld on the tactical battlefield. A number of new maps were also added to the tactical game, as well as multiplayer. The PC version of Enemy Within is an add-on that requires the base game Enemy Unknown.
XCOM: Enemy Within is the expansion to the 2012 Game of the Year award-winning strategy game XCOM: Enemy Unknown. Enemy Within adds an incredible array of new abilities, upgrades and weapons to combat new enemy and alien threats. This expansion also introduces new maps and missions, new tactical and strategic gameplay, and new multiplayer content providing a fresh new gameplay experience.