During the War
Maripony was built over the original home of Equestria's Diamond Dogs, Splendid Valley. A mine was built to get at the gemstone laden valley's resources. The Maripony facility was built over Splendid Valley, once it had been mined for all the gems. Maripony worked on numerous dangerous magical research, most notably, Twilight Sparkle's artificial alicorn project. The Valley and mines below Maripony became filled with hazardous materials and poisons generated from within the facility.
The Last Day
During the Last Day of the war, Maripony suffered a direct hit from a Balefire Megaspell. Twilight Sparkle was performing an experiment involving artificial alicorns, with Trixie as a willing test subject. Twilight was assisted by two other unicorns, Gestalt and Mosaic. During the experiment, Maripony was struck by the balefire megaspell, causing the facility to go into a lockdown. Trixie was knocked into the Vats of Impelled Metamorphosis Potion (I.M.P/Taint) that were used in Twilight's experiments.
Twilight Sparkle ended up trapped in a secure room, unable to escape. She was greatly weakened as she had run out of supplies and was slowly dying. The secure room she was locked in, was eventually forced open by Trixie who had become a powerful mutant, that claimed to be saving Twilight. Trixie dragged her into the Vats of Taint, absorbing her into the Unity.
The Diamond Dogs that kept returning to the Maripony area were mutated horribly, eventually becoming Hellhounds. The hellhounds broke into the Maripony armory, where they acquired an arsenal of magical energy weapons that they would modify so they could use them with their paws.
Maripony is the home of The Goddess and the unity alicorns. The goddess uses the taint vats inside to create more alicorn drones. The area around Maripony is heavily populated by Hellhounds, which continued to try to attack the facility long after the Great War. For the most part, The Goddess was able to drive hellhounds away by emitting loud, high-pitched noise from the facility's loudspeakers.
Maripony was destroyed when Littlepip uses a balefire bomb she acquired from Red Eye to destroy the facility. The Godesses's alicorns escaped the destruction of Maripony and the explosion itself was contained mostly by a powerful magical shield that the goddess erected. The Goddess was killed in the explosion, the hellounds in the surrounding area were also killed, leaving very few survivors. The Enclave's council member Harbinger was also killed, and a Thunderhead floating over Maripony was destroyed prompting the Enclave to launch an assault on the wasteland at large.
- Maripony is based on the Mariposa Facility from Fallout and Fallout 2
- The I.M.P/Taint Vats are based on the FEV Vats from the Fallout series
- The Goddess inhabiting Maripony is based on The Master from Fallout
- Maripony being struck by a Megaspell is a reference to West Tek Reserch Facility in the original Fallout. Unlike the Facility however the Maripony Survived and the Facility became The Glow.