Equus is a world devoid of humans and and home to sapient hoofed animals including ponies, buffalo, and cattle along many beings considered mythological on Earth-Prime such as dragons and griffins. Its most dominant nation is the Principality of Equestria, a traditional monarchy ruled by two alicorns, Celestia and Luna. Other nations include Zebrica, Saddle Arabia, and the Griffin Empire.
The demiplane of Equus is heliocentric, with Celestia and Luna moving the sun and moon. Both celestial objects are much smaller those in Earth's solar system. The stars are of a similar size, but constellations remain mostly the same as seen from Earth.
In its very early history, the ponies were split into three rival tribes: the unicorns, the pegasi, and the Earth ponies. The Archdevils took advantage of this by sending in the wendigos to feed on their conflict. The Elder Council responded by sending recruiting their own agents to convince the leaders of the nations to put aside their differences to stop the new threat. When the unicorns, pegasi, and Earth ponies succeeded in expelling the wendigos, they created the nation of Equestria. Shortly after, Celestia and Luna were made rulers of the land as they represented all three tribes.
Although Celestia and Luna were for the most part benevolent rulers, Luna became dissatisfied with her lack of popularity among the ponies, who disliked her fierce and boastful personality along with her association with the bat-winged night ponies. Luna was corrupted by the nightmare forces originating from the moon and became Nightmare Moon, a fearful entity who sought to overthrow Celestia and begin an era of everlasting night. In response, her sister banished her to the Moon.
During the year 2010 AC (Anno Celestia), Nightmare Moon escaped and sought to conquer Equestria. This time, she was defeated and redeemed by six ponies chosen to hold the Elements of Harmony, as Celestia was no longer able to use them. The bearers would later defeat other threats to Equestria and their leader, Twilight Sparkle, would become an alicorn princess herself.
- The other My Little Pony series take place in separate universes and all of them inhabitants who are analogous to the inhabitants of Equus.