Princess Luna

Princess Luna, formerly Nightmare Moon (known in legends as the Mare in the Moon), is the younger sister of Princess Celestia and the antagonist in the first two episodes of the series. Like her sister, she is a winged unicorn. She is transformed back to her former self by the Elements of Harmony and returns to her duty of raising the moon and stars over Equestria every night.

Personality
As Nightmare Moon, she was vengeful, condescending, jealous, and angry. The legend that is narrated in the first episode tells that these negative feelings harbored towards her sister turned Luna into Nightmare Moon in the first place. She appears much older and larger than her true self, and is comparable in size to Princess Celestia.

As Luna, she seems much more soft-spoken and gentle, and full of regret over her actions. She appears much younger and smaller, resembling the main cast of ponies. Little is known about her personality in this form, but she seems sad and remorseful when she appears in Ponyville. When the ponies present her with a wreath of flowers, she seems very touched and happy.

Lauren Faust has stated that Luna is not yet fully-grown, and that there was some evil magic which transformed her into Nightmare Moon. When Luna is fully grown, she will not look like Nightmare Moon.

Skills

 * See also magical abilities

Like her sister, Princess Luna possess magic far beyond normal unicorn ponies. She is able to control the moon and the night sky, bringing them out each night and then moving them away to make room for the dawn.

As Nightmare Moon, she is able to take on the form of objects and other characters, among them mist, thorns, and a trio of pegasus ponies who present themselves as The Shadowbolts, the doppelgänger of The Wonderbolts.

One thousand years ago
The legend narrated in the first episode tells that one thousand years ago, the day and night cycle of Equestria was ruled by two sisters: Luna, the younger, who brought the night, and Celestia, who brought the day. However, Luna grew jealous of her sister: the ponies of Equestria all enjoyed and loved Celestia's daylight, but were all asleep at night. No one was awake to appreciate the beautiful night she had worked so hard to create. Eventually, this jealousy and bitterness drove Luna to become Nightmare Moon, and prevent Celestia from bringing forth the sun. She intended to keep Equestria in eternal night. Her older sister, with great sadness and regret, stopped Nightmare Moon by using the Elements of Harmony, and imprisoned her within the moon. Henceforth she became known as the Mare in the Moon and knowledge of her slowly drifted to the area of myths.

Escape
Eventually, a thousand years passed. The studious Twilight Sparkle read about the legend which prophesied Nightmare Moon will return on the night of the Summer Sun Celebration, held in honor of Princess Celestia and the longest day in Equestria. As foretold, Nightmare Moon escaped and soon appeared in place of Celestia at the festival.

Twilight was the only pony, with the exception of Celestia, who anticipated Nightmare Moon's return; however, she did not warn anyone as Celestia encouraged her to use her time to make friends. Once again Nightmare Moon desired to bring forth eternal night upon Equestria. Twilight knew that only the Elements of Harmony could stop her, and set out on a quest to find them along with her five new friends: Applejack, Fluttershy, Rarity, Rainbow Dash, and Pinkie Pie. Overhearing this, the evil mare tried to stop them with different obstacles. After many hardships, the six ponies realized that their own virtues as friends were the true Elements of Harmony.

Using the six elements: honesty, kindness, generosity, loyalty, laughter, and magic, the ponies were able to transform Nightmare Moon back into Luna.

Forgiveness
Purged of her dark feelings, Nightmare Moon was transformed back into Princess Luna. Celestia offered to put the past aside and start anew, with the two of them ruling Equestria together as equals. Filled with remorse and shame for her actions, a tearful Luna apologized.

The two sisters were thus reunited and the balance of day and night was restored.

Luna was last seen at he end of episode two, attending Pinkie Pie's party by her sister's side. She seemed sad about what she had done in attempting to shroud Equestria in eternal night, but is cheered up when the ponies of Ponyville welcome her.

Season two
Princess Luna has not made any subsequent appearances in season one. According to the show's creator, Lauren Faust, Luna is set to return sometime in season two.

Luna was prominently mentioned in the The Return of Harmony Part 1, in which Princess Celestia tells the ponies of the time in which she and Luna bonded together with the Elements of Harmony to defeat the mischievous Discord and forever imprison him in stone, restoring order to Equestria.

Appearances

 * See also character appearances


 * S1E01: Friendship is Magic, part 1 as Nightmare Moon
 * S1E02: Friendship is Magic, part 2 as Nightmare Moon and Princess Luna

Gallery

 * Princess Luna and Nightmare Moon image gallery

Trivia

 * Princess Luna, alongside Princess Celestia, were both based on the G1 Princess Ponies from the 1980s animated series.
 * Luna's name in Latin refers to the moon. Interestingly, the Friendship is Magic book, which comes with one of the gift sets of the toys, references her as Selena, "selene" (Σελήνη) meaning "moon" in Ancient Greek. More specifically, Luna is the Latin name for the Greek moon goddess Selene, who is the daughter of Hyperion and Theia in Greek mythology. Additionally, in the European French dub, Nightmare Moon was renamed as La Jument Séléniaque, which literally means "The Selene Mare."
 * When imprisoned in the moon, Luna appears as a dark area on the moon's surface. A similar shape in astronomy is called a lunar mare (Latin for "sea", pronounced "mah-rey").
 * Nightmare Moon's title - "Mare in the Moon" - is a play on the mythological Man in the Moon.
 * Princess Luna and Princess Celestia raising the moon and sun respectively is based on Norse mythology, where the horses Hrímfaxi and Skinfaxi are believed to be responsible for pulling the moon and sun across the sky respectively.