Mass Effect 2
The research team, led by Dr. Amanda Kenson, built Project Base around a Reaper artifact they discovered embedded in the asteroid. The team's original intent was to study the artifact, dubbed "Object Rho", but when visions emitted by the artifact convinced them that a Reaper invasion was imminent, they started what they called "the Project". The researchers believed the Reapers planned to use the Alpha Relay to strike anywhere in the galaxy; in order to prevent this, the relay had to be destroyed. To that end, Dr. Kenson and her team obtained scrap engines and navigation technology through sources on Omega and installed them into the asteroid. Once complete, the team could send the asteroid hurtling into the Alpha Relay with the press of a button.
Sometime during their study of the artifact the entire team was indoctrinated. Eager to witness the Reapers' arrival, the team no longer wished to complete "the Project" and launch the asteroid.
After Dr. Kenson's capture by batarian forces during a scouting mission, Commander Shepard rescues her. Upon returning Kenson to Project Base with less than two days before the Reapers arrive, Shepard realizes that Kenson and her team have been indoctrinated by Object Rho. Although Shepard fights tenaciously against wave after wave of Project Guards, Engineers, Elites, Pyros, and a YMIR Mech, eventually either the Commander is overwhelmed by the Guards, or the Reaper artifact unleashes a wave of energy which knocks Shepard out. Shepard awakens two days later with only a few hours remaining to initiate the Project. Despite the research team's heavy opposition and an attempt by Dr. Kenson to overheat the Base's fusion core and destroy the Project's propulsion systems, Shepard manages to activate the Project and escapes the Bahak system moments before the Alpha Relay is struck and destroyed by the asteroid, taking the entire system with it.