The Master

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 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.

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.

Trivia

• The Master takes his name and M.O. from the Big Bad of the original Fallout.