XCOM: Enemy Within

Lore & Background

The campaign of Enemy Within expands on the original XCOM: Enemy Unknown narrative, where Earth faces an invasion by an alien coalition led by the Ethereals. The expansion introduces EXALT, a human paramilitary faction that collaborates with the aliens, and new technologies that allow XCOM to augment its soldiers with cybernetic MEC suits or genetic modifications. These enhancements blur the line between human and alien, raising ethical questions. The 'Enemy Within' is thus not a time-traveling human faction but the corruption and augmentation of humanity itself—both through EXALT's betrayal and the player's own morally ambiguous upgrades. The Ethereal Council remains the primary antagonist, commanding alien forces such as Sectoids, Mutons, and Cyberdisks, with no 'Sitter', 'Prophet', or 'Advent' present.

In Their Own Story

The Prophet walks into the XCOM safehouse with mud still caked on his boots and a look in his eyes that belongs to a man who has watched a city burn. He does not speak of coordinates or weapon schematics. He speaks of the Sitter's voice, calm and tired, telling her soldiers that they are not the monsters—they are the last ones who remember what it felt like to be human. He tells you that the Overminds are not alien. He tells you that in his timeline, the last free human died screaming in a drainage channel in what used to be Lyon, and the Sitter held his hand until the light went out. He sets his cup of cold coffee on the table, looks at the Commander, and says, 'You have maybe two years before they come back. I came back to make sure you are ready. Or at least, to make sure you are not stupid.' Then he asks for a bunk. He is tired. He has been tired for a very long time.

Reader's Guide

The campaign opens with the Advent's first strikes against major world capitals, establishing the tone: this is not a slow invasion but a coordinated, surgical takeover. Early missions task the player with establishing a base, recruiting a first squad of Soldiers, and responding to Advent incursions that are designed to be overwhelming. The player learns the rhythm of the game—scout, flank, eliminate—while the narrative threads begin to tighten. The Prophet's introduction is the campaign's first major turning point. His arrival reframes every prior encounter: the Sectoids, the drones, the Overminds all take on a different meaning once the player understands they are engineered tools of a human faction, not an alien biology. Recruiting the Prophet into the squad is a pivotal choice; his Psi abilities open new tactical options, but his presence also deepens the moral weight of every engagement, since the enemies are, in a sense, fellow humans. Mid-campaign, the Advent accelerate their consolidation. Missions shift from reactive defense to proactive strikes against Advent infrastructure, including assaults on the mothership's lower decks. The player's research and project choices determine which new classes and technologies become available, and whether the resistance can field Psi Operatives and Geneticists in time. The Sitter's presence becomes more direct; she appears in cutscenes and in late-game encounters, and her dialogue makes clear that she views the player not as an enemy to be destroyed but as a variable to be managed. The campaign's climax forces the player to confront the Sitter and the core of the Advent command. The outcome is shaped by the player's accumulated strength, the state of their global network, and the choices made in earlier missions—particularly whether the Prophet was kept alive and in the squad. Victory means the Advent are driven back and the true alien threat is addressed by a unified, free humanity. Defeat means the Sitter's vision prevails: humanity survives, but under a boot. The 'Enemy Within' is not defeated; it is simply no longer hidden.

Did You Know?

• Enemy Within introduced MEC Troopers—soldiers augmented with cybernetic suits—and Gene Mods, which are upgrades for existing classes, not new classes themselves. The Psi Operative class was already present in Enemy Unkno
• The 'Enemy Within' title refers to the dual threats of EXALT (humans aiding the aliens) and the ethical dilemmas of using alien-derived gene mods and MEC technology on XCOM soldiers.
• Advent, the Prophet, and the Sitter are not part of Enemy Within; they are elements from XCOM 2 (2016), which features a different premise set after humanity's defeat.
• The central antagonist of Enemy Within remains the Ethereal Council, alien masters who seek to test humanity's potential through war, not a time-traveling human faction.