Brenner, who allegedly worked for the US Department of Energy, was a government figure steeped in mystery and controversy. He was a research scientist, and the Director of Operations at Hawkins National Laboratory until November 1983. He had a major role in various controversial experiments and programs, including Project MKUltra.
In 1959, Brenner was contacted by a fearful woman concerned by the strange behavior of her son, Henry. After she and her daughter were found dead at her house, and the patriarch Victor presumed to be the murderer, Brenner convinced government higher-ups to let him take Henry into his custody. After learning Henry possessed dangerous psychokinetic abilities, Brenner figured out how to disable them with an implanted chip, while also reproducing these abilities in a number of child test subjects at Hawkins Lab, including Eleven.
On September 8, 1979, Brenner's fears about Henry came true when he manipulated Eleven into removing the suppressant chip, and proceeded to go on a murderous rampage throughout the facility using his restored abilities. Brenner was indirectly knocked unconscious during the attack, and was shocked to discover the massacre of his 'children' and colleagues upon awakening. He later learned Eleven, the sole survivor of the massacre, had somehow defeated Henry, causing him to mysteriously vanish. Brenner was impressed by Eleven’s feat, but was disappointed when she proved unable to reproduce the same raw strength upon waking from her coma.
In the years that followed, Brenner tested the limits of Eleven’s abilities through various experiments. In November 1983, Brenner’s experiments indirectly unleashed a monster from another dimension into Hawkins, allowing Eleven to escape the lab. In the following week, Brenner and his team searched for Eleven while investigating the newly opened gateway to the other dimension (informally known as the Upside Down). This culminated in an unsuccessful attempt to capture Eleven at Hawkins Middle School, which drew the attention of the monster. Brenner survived the monster's attack and sustained only minor injuries, but was unable to return Eleven to the lab.
Following the events of November 1983, Brenner was ousted as the lab’s director, and replaced by Dr. Sam Owens. The lab was shut down in 1984, and Brenner was falsely presumed deceased.
By 1986, Brenner and Dr. Owens had established the Nina Project, situated at a top secret facility in the Nevada desert. The project was conceived in response to Eleven losing access to her psychokinetic abilities, and was designed to reactivate her powers via an experimental procedure. Brenner and Owens wished to use Eleven's abilities to stave off the continued existential threat posed by the Upside Down. After some initial hesitation, Eleven participated and ultimately regained her abilities.
Brenner sought to continue the experiments, wanting to push Eleven's abilities beyond their previous limit. Brenner and Owens began to argue when Eleven insisted on returning to Hawkins, which provoked Brenner to forcefully incapacitate both Eleven and Owens. Shortly after this, the US Military arrived and commenced a full-scale attack on the facility; Lt. Col. Jack Sullivan believed Eleven to be the root of the issues plaguing Hawkins, and sought to eliminate her.
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