|“||I know you think I'm a monster. And you're right. Not a day goes by where my dreams aren't haunted by what I did to David.||„|
|~ Archer outlining how he feels about abusing his brother|
Dr. Gavin Archer is the main antagonist of the Overlord DLC in Mass Effect 2. He was a Cerberus scientist who run a Cerberus Project called "Overlord". This project was a means on how to control the geth. After observing his autistic brother, David's intelligence and ability to communicate with them, he had him forcibly incorporated to the Geth VI to figure out a way to control the Geth. The experiment eventually went horribly wrong due to David's mental instability and the torture. The Geth had gone berserk and started killing the Cerberus staff, until the two brothers were the only survivors.
Archer was a ruthless and ambitious scientist. Because of the Illusive Man's great intolerance of failure, he became increasingly desperate to find a way to prevent a war with the geth. He believed that sometimes you had to ignore the risks of a situation and simply take a chance, comparing his experiment to Shepard's own attempt to find the Reapers. When the atrocities behind his experiment were revealed, he defended his actions, saying he was desperate and that the experiment seemed harmless at first. He also claimed that he lied to Shepard out of necessity, saying if he had told him/her the truth, he/she would have shut him down instead of David.
Despite his ruthlessness and attempts to justify his actions, Archer was not callous and showed genuine concern for the casualties his experiment caused, admitting that it had cost 'more souls than [would] ever forgive [him]'. He also described what he had done to David as 'unethical'. Nevertheless, he refused to take full responsibility for these, believing it to have been worth it if it spared 'a million mothers mourning the loss of a million sons'. When Paragon-Shepard attempted to take David away, Archer tried to stop him/her, believing him to be too valuable. Even Renegade-Shepard was disgusted by his actions, calling him a 'sick bastard'.
After leaving Cerberus, Archer was saddened deeply by what he had done to David, holding onto a vain hope that one day he could beg his forgiveness. He claimed that he was haunted every day by what he had done and that Shepard was right in saying he was a monster. If lied to by Renegade-Shepard that he had died, Archer was so devastated that he went away to kill himself. Before walking away, he said to Shepard 'God be with you, Commander. He was never with me.'