The Master, formally Richard Grey, was the leader of the Super Mutants in Angela, and the originator of the Unity. When the Master was human, he joined an expedition along with Harold to explore Mariposa Military Base in northern Angela in order to stop its mutant threat. It was there that he fell into a vat of FEV after getting hit by a crane and was transformed by it into a Reuniclus. Over the years he absorbed numerous humans and Pokémon alike, becoming a true monstrosity and making a new home in the Cathedral, where he fused with the Overseer's chair and became techno-organic, his gel taking up a good portion of the lower floors.
He eventually met his end upon meeting Tagg and his group, who more or less drove him to suicide by pointing out that his Super Mutants were completely sterile, causing him to self-destruct the Cathedral with a nuke hidden underneath.
The Master was a powerful psychic, capable of sending mental orders to his Super Mutants throughout Angela, and surrounded himself with a field that would cause massive mental damage to anyone who enter his corridor without proper protection. For surveillance he was also capable of synthesizing the parts of beings he'd absorbed as extra eyes, ears, etc. The Master also had Gatling lasers neuro-linked to his biomass, for killing anyone who managed to get past his other defenses. The large amount of minds he had also likely rendered him mostly immune to any sort of mindreading.
- The Master takes his name and M.O. from the Big Bad of the original Fallout.