Indoctrination

Indoctrination is the term used for the "brainwashing" effect the Reapers and their technology have on organic beings. A signal or energy field surrounds the Reaper, which subtly influences the minds of any organic individual in range. It was first reported by farmers on Eden Prime, who claimed there was a "horrible noise" emanating from Sovereign as it descended. Matriarch Benezia said that even Sovereign's interior serves indoctrination: the strange angles of the rooms are confusing and make you uncertain of yourself.

The mental damage from indoctrination is severe and permanent. Only people with immense mental strength are able to resist indoctrination, and even then, only for a short time. Matriarch Benezia used her abilities to keep a 'haven' in her mind free of indoctrination, hoping for a chance to use it, but this meant she was effectively trapped in her own mind, watching in horror as she committed atrocities on Saren's orders. When mortally injured on Noveria, a despairing Benezia refused Shepard's offer of help and chose to die, saying "I am not myself, I never will be again."

Indoctrination is one of the most insidious weapons the Reapers have in their arsenal. As Vigil explains, indoctrinated slaves from conquered planets were used during the last Reaper incursion as sleeper agents. They were taken in by other Protheans as refugees, then betrayed their own people to the machines. But the Reapers viewed them as disposable. When they disappeared back through the Citadel relay, the Reapers abandoned their indoctrinated slaves, leaving them to starve or die of exposure.

The precise mechanics of the indoctrination effect are poorly understood. It is believed that the Reapers generate an electromagnetic field, waves of infrasound and ultrasound, or both in order to stimulate areas of a victim's brain and limbic system. The resulting effect varies depending on the intent of the Reaper: the victim may suffer headaches and hallucinations, have feelings of "being watched" or paranoia, or come to view the Reaper itself with superstitious awe. Ultimately, the Reaper gains the ability to use the victim's body to amplify its signal, manifesting as voices within the victim's mind.