When Nightmare Moon (Princess Luna) was freed from her imprisonment, a piece of her magic broke off from the moon. From this piece emerged a “pegasus” named Lunar Darling, who bears a slight resemblance to Nightmare Moon. She is not actually a pony, but rather a semi-physical manifestation of magic in the form of a pegasus, plus, her “cutie mark” isn’t functional, it’s just the part of Nightmare Moon. Lunar Darling is unable to use her wings, and they remain dangling on the ground. Additionally, Lunar Darling cannot appear outdoors during the day, and she digs a burrow before the moon sets, hiding there until the sun rises. Also she has a weak aura that she uses to unconsciously put the ponies around her to sleep. With the help of euthanasia, she can possess a sleeping pony. But she doesn’t want to harm anyone, really, and doesn’t know why and who is she. And she’s sleepy.