Stable 91 is Stable-Tec Stable that was built beneath the snow in Northern Equestria. It is one of at least six other Stables that are known to have been constructed in the North. Stable 91 appears in Fallout: Equestria - Rising Dawn.
Stable 91 is equipped with a General Arcanics Spark Generator, and a Stable-Tec water purifier with an integrated Water Talisman. This Stable was designed to maintain a population of 300 earth ponies, unicorns, and pegasi. Stable 91 is led by a traditional Overmare.
Stable 91 was built prior to the dropping of the balefire bombs throughout Northern Equestria. Its population was selected via a lottery which chose a mix of the pony races, excluding the batponies, in Stable 91, among other Northern Stables. Stable 91's population survived beneath the earth, and the bomb shelter was a success.
In Fallout: Equestria - Rising Dawn, Stable 91's Water Talisman is destroyed when its water purifier overloads. Why this occured, it is not known, but the machine's failure was attributed to simple mechanical failure or faulty equipment. Overmare Peach Petals sent out an expedition outside the Stable's doors in search of a Water Talisman.
The expedition, consisting of Red Dawn, Dew Drops, Amber Fields, Box Cutter, Lightning Twirl, and Star Glint, left the Stable the very next day en route to Poneva, which their Overmare believes, may still have Water Talismans stored in the Stable-Tec facility there.