Lonesome Road, the final DLC for Fallout New Vegas, reveals the origin of Ulysses — the courier who refused the chip delivery that started the entire game. The Divide was once a thriving settlement that Ulysses called home, and the Courier destroyed it without knowing, by carrying an old Enclave warhead detonator in a package through the area years before the game’s events.
The detonator triggered buried nuclear warheads, destroying the Divide, killing everyone Ulysses cared about, and creating the wasteland of tunnellers and marked men that defines the DLC’s landscape. The Courier did this as a mundane job. The apocalypse was a delivery.
Ulysses spent years tracking the Courier to understand how someone could commit that act and simply walk away unchanged. His entire philosophy — flags, symbols, nations, history — is built around the incomprehensibility of what was done without intent.
The most devastating detail: the package that caused the destruction is listed in the game’s data as ‘Package 7’ — the same package number given in the intro cutscene when the Courier is described as being hired for a job. The destruction of the Divide was the job before the job that started the game. Obsidian planted this four DLCs deep.

The environmental storytelling in this game is on another level. Thanks for documenting it so clearly.
The detail work the devs put into areas most players never visit is what separates great games from good ones.