After an expedition gone wrong while searching for the source of hostile mutants attacking nearby settlements, a man by the name of Richard Grey found himself stuck in one of the FEV vats for an extended amount of time after the others in his group with the exception of Harold were killed, and due to his being born in a vault and being relatively radiation-free, Grey underwent the most unique of FEV mutations, turning into the antagonist of the Vault Dweller most popularly known and referred to as "the Master". As the Master began experimenting with FEV and using other humans to expand his biomass, the Master soon came to the conclusion that FEV could be used to evolve and unify humanity in order to save themselves. However, the Master hit an obstacle in that most humans were coming out as