In order to avoid the self-destruction of the species, the Master desired to forcefully evolve humans into one, perfect race, removing the inequalities that are the cause of strife among humans. To this end, he used the Forced Evolutionary Virus (FEV) to create his race, the super mutants, also called the Master's Army.
With the discovery of the Los Angeles Vault, and the establishment of the Children of the Cathedral, the Master created the means of conversion and recruitment of people into his project. Under the disguise of apostles of peace, establishing hospitals and churches in the cities of the wasteland, the Children and the Mutants, led by the nightkin elite warriors, prepared for a war that would change the face of the Earth and bring upon the master's dream.
However, according to the Master's personal Audio Log, he also had a different vision on the Unity's true goal, the one that involved merging humanity together. Literally. It is known that using FEV, Master was absorbing both organic and technical material into himself, growing larger and larger. The creatures he absorbed not only became his biomass, but also their very minds were merged with the Master.
It is possible that this discrepancy is due to the Master having multiple personalities at this point, each with different ideas of what the future of humanity should be. Another possibility is that the Master considered both visions of the Unity to be perfect at the same time, desiring to see both the world of super mutants and himself, expanding to new minds and bodies.
The Unity was destroyed before it could be created, by the Vault Dweller, who defeated the Master and engineered the destruction of his research center as well as the Mariposa Military Base, preventing any chance of the project ever succeeding. Regardless, even if the Master did succeed, the Unity would fail, as the FEV rendered the super mutants sterile and the Unity would bring about the final end of humanity.
As for the Master's followers, the super mutants split into several different groups. A very large group traveled East, reaching as far as the Midwest, becoming Gammorin's Army. Another group was noted as traveling North, some (like Marcus) settled down to coexist with humans, and some small groups still wander the wastes attacking all non-super mutants.
The Unity was composed of several persons, organizations and sub-organizations working together. The head of the Unity was the Master himself. The Unity consisted of:
- Master's Army - the army of the perfect creatures the Master was dreaming to reproduce. It's composed of normal mariposa super mutant, centaurs, floaters and nightkins, the elite forces of the Master.
- Children of the Cathedral - human servants of the Master and followers of his vision, consciously or not. They are called "little brother" by super mutants.
The Unity, as a goal and an organization, appears only in Fallout. However, it is mentioned in Fallout 2, Fallout: New Vegas, Fallout Tactics and Fallout: Brotherhood of Steel. Some characters from these games, notably Attis and Erkal, were aimed to resurrect the Unity's purpose, but failed.