Many centuries ago, in the distant mists of ancient time, a disaster shook the planet called Equus. The skies were charred with fiery blasts, and poisonous rivers flowed throughout the land of Equestria. Ponies who once gazed upon glorious skies and breathed pure air, were forced to find a way to survive. They found that way under their feet..under the ground. Canterlot became the capital city of the underground world. In their subterranean existence, the era of the magic of friendship passed them by. Perhaps the ponies even forgot what the sky looked like. Sunset, a member of the Canterlot Rangers, witnessed a mysterious event while checking out a Bio-chem company facility during a routine patrol in Canterlot that would change the outcome of the underground world of Equestia and her life...Thus begins the story of deep Equus.

Crossover: (mlp x Breath of fire: Dragon Quarter )