The Pluto was one of Umbrella's failed bioweapons experiments. It shares its name with the Roman god of the underworld.
Originally a condemned criminal only known as "α" (Alpha), what would become Pluto was subject to numerous experiments.
On the first day of the experiment, a metal rod was hammered into his frontal lobe to alleviate pain. On the fourth day, his eyes were removed to test how his other senses would react.
Later into the experiment, he would gain mass, becoming overweight around the time he was given steroids to improve his muscles. Despite his immense size, he is also incredibly fast and his acute hearing makes him very accurate.
The experiment was suspended on day 41 after "α" managed to escape, killing five guards in the process. He would meet his demise at the hands of Bruce McGivern, a government agent sent to arrest a Bioterrorist.