When Princess Celestia used the Elements of Harmony against her sister, Luna, she only banished Nightmare Moon to the moon, and Luna to a different Earth.

Now Luna has to wander what's left of the great city of New York, ten years in on the Cordyceps Brain Infection epidemic.

(I'm esimating that Celestia is in her mid thirties, and Luna in her mid twenties in the show. Now minus ten years, and Luna is about three years younger than me.)

WARNING! Contains Blood and Gore, Intense Violence, Language, Alcohol Use, and Disturbing Content.