: To end the threat, the fireteam must descend into the heart of a massive Xenomorph hive to destroy the source of the infestation once and for all. The "Pathogen" Expansion

: The marines descend to LV-895 to investigate Weyland-Yutani ruins and locate another survivor, Cynthia Rodriguez . They discover that the corporation has been experimenting with the Pathogen to create mutated Xenomorphs.

Released after the main game, this expansion continues the story as the Endeavor crew explores a new, unexplored Engineer ruin ravaged by a deadly infection. It introduces enemies and a hive unlike anything previously seen.

The game's story is divided into four distinct campaigns, each consisting of three missions: