The Vault Dweller was a god, summoned to the world to save people. Born about 2077 years before the Great War (0 A.D), the Vault Dweller was Jesus. Unfortunately, in the world of Fallout, the Vault Dweller fucked women a bit too much. It was a bad habit that he could not stop. When the Master was put into his mind, he gathered 3 towns (Junktown, Hub, Horny Sands) to kill the murderer.
After he accomplished, he built a tribe to the north, otherwise known as Arroyo. It was dedicated to pussy. After 20 years of living in his city, he got a massive boner and decided to search for some new ladies to enter. He was never heard from again.