|This article is about the Cerberus project. For the Mass Effect 2 DLC, see Overlord.|
Mass Effect 2 EditDavid Archer, chief scientist Dr. Gavin Archer's brother, volunteered for the experiment to meld his mind to a VI. The VI overwhelmed David and the resulting hybrid essentially became a virus, which proceeded to take over the facility and used the live geth that had been acquired for the project to kill off the Cerberus staff in Hermes, Vulcan, Prometheus, and Atlas Stations.
The VI attempted to leave Aite through the facility's communication dish, but the dish was destroyed by Commander Shepard. If it had escaped, potentially every electronic device in the galaxy accessible by the extranet could be subsumed and used by the VI against an unsuspecting populace.
The VI itself was designed by Cerberus to exploit the religious tendencies of the geth. This was inspired by Cerberus' observations of Saren Arterius as a leader of the geth in the events leading up to the Battle of the Citadel. The researchers hoped that the hybrid VI, essentially a "computer program with a face", could become a similar kind of figurehead and thus give Cerberus complete control over all geth.
It is later revealed that David Archer, the human component of the hybrid VI, was autistic and a mathematical savant. David's unparalleled understanding of mathematics allowed him to communicate with the geth on a fundamental level; communication had previously been a significant hurdle for the project, and without any results the Illusive Man threatened to shut the project down. Dr. Archer realized the potential of this breakthrough, and forcibly incorporated David into the VI. At this point, the hybrid VI went berserk and began its rampage and escape attempt.
After deactivating the rogue VI, Shepard's decision about who should handle the care of David Archer determines if Project Overlord will continue or be decommissioned.
Mass Effect 3 Edit
If Shepard frees David, Gavin starts feeling regret over being involved in Project Overlord. Thus, he chose to erase all information on the project and left Cerberus. Shepard also meets David during evacuation of Grissom Academy along with Octavia and Isaac who use a barrier to protect themselves from Cerberus troops. David will then open the nearby door to the armory for Shepard.
If Shepard chose to continue Overlord, Gavin reveals that, as the test continued, David began communicating better and better before suddenly becoming catatonic. Out of regret and feeling it was the only way, he killed his brother to end his suffering and fled Cerberus. He gives Shepard the Overlord results.
Should Shepard choose not to investigate Project Overlord, Gavin states that the situation in the research facilities eventually grew out of control and he was forced to detonate its nuclear failsafe device, which destroyed the whole base.
It is also revealed that the geth had been eavesdropping on Cerberus regarding Project Overlord. The synthetics have refined the human/VI interface into a much safer construct. Instead of intrusive body probes as was done with David Archer, the geth version of the interface takes the form of an easily-deployable man-sized pod that scans its occupant, requiring only a minimum of movement during the initial mind upload. Legion (or the Geth VI) constructs such a device incorporating Normandy equipment on Rannoch if Shepard embarks on a mission that requires entering the geth consensus.