As a big fan of fallout i tried to do something :v
Small story i just made up, it takes after Fallout 1 ending time-wise (Since i saw it was optional and could be fun :v).
(Sorry English, it's my 4° Language there may be lots of errors)
After being exiled from his vault and having found the city of Arroyo, he got told that the radiation emanated from the Mariposa military base where previously he exploded the vats, from which the super mutant were born, created a rift between two worlds. So he went to investigate about this rift and right after he tried to touch it he got sucked in and the rift closed right after, unable to return to his world the vault Dweller was confused from this new world, full of life and not destroy'd from human stupidity, but one thing was certain, there was a strange feeling of war.. short after he heard from the citizen that there was a three-way war across the borderland he found himself, the vault Dweller thought while sighing: "War.. war never change".