Princess Luna, formerly known as Nightmare Moon or Night Mare Moon, is a Alicorn, the younger sister of Princess Celestia, and is the main antagonist (as Night Mare Moon) of the first two episodes of My Little Pony Friendship is Magic. Luna is restored back to her former self through the magic of the Elements of Harmony and returns to rule Equestria alongside her older sister.
Princess Luna's appearance has changed dramatically since Mare in the Moon. She has become considerably larger (roughly 50% bigger than a regular pony, but still smaller than Celestia), her body is a darker shade of blue and her mane now ripples and sparkles, like the night sky. Her old design is still used in the promotional online game Canterlot Castle, and her old mane is partly visible in some of the shots in Luna Eclipsed. Lauren Faust has stated that when Luna is fully grown, she will not look like Nightmare Moon.