Princess Luna is a fictional character from My Little Pony: Friendship Is Magic, the younger sister of Princess Celestia and co-ruler of Equestria, responsible for raising the moon and entering ponies' dreams. Initially an antagonist named Nightmare Moon due to jealousy, she was defeated and reformed, becoming a beloved recurring character who helps her subjects with their nightmares. She is a winged unicorn with a dark blue coat, light blue eyes, and a flowing, starry mane and tail. 