The Courier had explored the whole of the Big Empty. The X-13 Stealth Research center, the X-8 Cyberdog research center, the Y-17 Medical facility, and many more places.

Or, at least he thought he has explored everything. But soon the Courier realised he had left one path unexplored: Outside of the radar fence.

And so the Courier starts on another adventure, in which he will explore the seemingly endless P-0 research center, and the scientific… and magical… wonders within.

Crossover with Fallout: New Vegas. This is not, I repeat, NOT in any way related to Fallout: Equestria. Marked Alternate Universe as the DLC and game itself had multiple endings.

This acts as if the Courier did not bomb anyone in Lonesome Road, saved both Doctor Mobius and the Think Tank, did all side quests in Big MT, and went with the NCR. Also assuming the Courier is male and other things.