Princess Luna

Princess Luna, formerly Nightmare Moon or Night Mare Moon, or Mare in the Moon, is an Alicorn pony, the younger sister of Princess Celestia, and the primary antagonist of the first two episodes of My Little Pony Friendship is Magic as Nightmare Moon. The Elements of Harmony restore Luna to her former self, and she returns to rule Equestria alongside her older sister.

Development and character design
The word "Luna" means "moon" in Italian and Spanish (in both cases, derived from Latin). The Friendship is Magic storybook, which is included in the Friendship is Magic Gift Set and Pony Friends Forever Pony Scooter Friends Daisy Dreams &amp; Rarity bundles, refers to her as Selena, "selene" (Σελήνη) meaning "moon" in 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. In the European French dub, Nightmare Moon is named La Jument Séléniaque, loosely translated as "the mare Selene" or "the Selene Mare". Her title in Twilight Sparkle's book in Friendship is Magic, part 1, "Mare in the Moon", is a play on the mythic story Man in the Moon. According to Lauren Faust, Nightmare Moon was originally named "Discord", a name which would later be given to another villain.

Princess Luna's appearance changed in subsequent appearances after Mare in the Moon. Her body is a darker shade of blue, and her mane is partially translucent, rippling and sparkling like Celestia's. 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. She also stated that when Nightmare Moon was defeated, Luna was reborn with very low magic levels. In newer episodes, her hair was then magical and wavy again because her good powers had been restored.

A pony based on Luna's design is used in Sweet and Elite. One of the show's layout artists suggested that the tall, slender build may have been used to give the pony a supermodel-like appearance.

Ruling Equestria
Princess Luna is introduced in the prologue of the first episode, depicted in a series of medieval-like drawings with a narration that says "Two regal sisters who ruled together and created harmony for all the land", and "The eldest used her unicorn powers to raise the sun at dawn. The younger brought out the moon to begin the night."

Nightmare Moon
The narration continues by stating: their subjects, the ponies, played in the day but "shunned" the night and slept through it, which made the younger Alicorn grow bitter, eventually refusing to lower the moon to make way for the dawn. Her bitterness "transformed her into a wicked mare of darkness: Nightmare Moon." The elder sister reluctantly harnessed the power of the Elements of Harmony and "banished her permanently in the moon," taking responsibility for both sun and moon, maintaining harmony in Equestria.

The name incorporates several plays on words: "mare" as in a female horse, "night mare" as in a mare of the night, and "nightmare" as in frightening dream, derived entirely from the medieval demon which haunts a person's mind with the use of horrifying visions. In addition, 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").

Following the prologue, Twilight Sparkle reads of a prophecy that states that "on the longest day of the thousandth year the stars will aid in her [The Mare in the Moon's] escape, and she will bring about nighttime eternal", though Spike dismisses it as "an old ponies' tale". While composing a letter to Princess Celestia warning her of the danger, an image of Nightmare Moon is reflected in a giant hourglass that Twilight passes by. The day of Nightmare Moon's return is also the thousandth day of the Summer Sun Celebration, so Princess Celestia sends Twilight to oversee the celebration's preparations which are held in Ponyville, and encourages Twilight to "Stop reading those dusty old books" and make some friends. The events of the first and second episodes revolve around Twilight Sparkle and her new friends' attempt to defeat Nightmare Moon by finding and using the Elements of Harmony, while Nightmare Moon tries to stop them in various ways. At the end of the second episode, Twilight and her friends confront Nightmare Moon and transform her back into Princess Luna, and she emotionally accepts Princess Celestia's offer to rule by her side again.

The show's developer, Lauren Faust, explained in a comment on her deviantArt page that Luna could not have been "drawn" from Nightmare Moon for a thousand years, and that Princess Celestia "did what she could" to orchestrate breaking the spell that turned Luna into Nightmare Moon. Faust added that this explanation is "as far as [she] ever got with it", and that the explanation might unfold differently on the show.

The season four premiere explores Princess Luna's transformation into Nightmare Moon in minor detail. A flashback Twilight experiences shows Princess Luna talking to Celestia, refusing to stand idly by while the ponies basked in Celestia's "precious light". She angrily declares that she would be the only princess in Equestria, and during an eclipse, she transforms into Nightmare Moon.

Nightmare Moon attacks Celestia with her magic, destroying portions of the old castle in the process. When Celestia retaliates with the Elements of Harmony, they prove too powerful for Nightmare Moon, and she is banished to the moon.

Prior to ruling Equestria
Princess Luna doesn't make any further appearances in the series until Luna Eclipsed, which aired exactly one year after her previous appearance. However, more of her history is mentioned in The Return of Harmony Part 1. In the episode, Princess Celestia tells Twilight Sparkle and her friends that she and Luna discovered the Elements of Harmony and used them to turn Discord, the Spirit of Chaos and Disharmony, into stone. Discord's spell is later broken because, as Celestia explains, "Luna and [herself] are no longer connected to the elements." In The Crystal Empire - Part 1 it is mentioned that she and Celestia worked together to defeat King Sombra, turning him into a shadow with their magic and imprisoning him in the frozen north. Luna's role in the confrontation with Discord alongside Celestia is shown in minor detail in Princess Twilight Sparkle - Part 2.

Twilight's Kingdom - Part 1 confirms that Luna was an associate of Star Swirl the Bearded during the Pre-Classical Era. Along with Celestia, she was involved in the defeat of the evil centaur, Lord Tirek.

Nightmare Night
Despite most ponies not recognizing Nightmare Moon upon her return, the episode Luna Eclipsed shows the ponies celebrating an annual festival called Nightmare Night, where foals go door-to-door in costumes collecting candy, which they later offer to the effigy of Nightmare Moon. Zecora tells in verse of the legend of Nightmare Moon, which explains the customs of the holiday:
 * Every year we put on a disguise
 * To save ourselves from her searching eyes
 * But Nightmare Moon just wants only one thing
 * To gobble up ponies in one quick swing
 * Hungrily, she soars the skies
 * If she sees nopony, she passes by
 * So if she comes and all is clear
 * Equestria is safe for another year
 * Fill up her belly with a treat or two
 * So she won't return to come eat you

When Princess Luna returns after her thousand-year absence, she is still mistaken by Spike and others as Nightmare Moon, especially by Pinkie Pie, who rouses up a gaggle of foals by shrieking at misconstrued acts of violence perpetrated by Princess Luna.

Although she originally intended to change the festival into a "bright" celebration, at the end of the episode Luna accepts Nightmare Night for what it is: a night of innocent scares, harmless pranks, and lots of candy.

Personality as Nightmare Moon
Much like the archetypal, over-the-top villains, Nightmare Moon is overly confident of herself and dramatically declares that the protagonist is a fool (foal) for thinking she can defeat her, and that "the night will last forever".

Bitterness
The narration at the beginning of Friendship is Magic, part 1 speaks of Nightmare Moon's bitterness which transformed her. When she first appears, she intimidates the ponies with her evil laugh and pointed questions. She snidely refers to the ponies as her "beloved subjects", but appears genuinely impressed when Twilight Sparkle recognizes her as Nightmare Moon.

Manipulation
Nightmare Moon uses her magic to set obstacles in Twilight and her friends' path to the Elements of Harmony indirectly, making creatures unwittingly assist her. These include the manticore whose paw she embeds with a thorn so he'd attack the ponies, or the sea serpent whose mustache she cuts off so he'd make the river impassible. She further indirectly attacks the ponies by causing a cliff side to collapse underneath the ponies' hooves, and by making trees appear as monsters. As the Shadowbolts, she tries to persuade Rainbow Dash to abandon her friends so they won't be able to cross a fallen bridge and reach the Elements of Harmony.

Despite her indirect approach, when she is attacked by the royal guards, she quickly repels them with lightning, then turns into mist and floats away. She also confronts Twilight Sparkle directly when the two charge at each other, right before shattering the Elements of Harmony.

Remorsefulness
Once transformed back to her former self, Princess Luna is remorseful and tearful upon seeing her older sister. She runs to Celestia's side, apologizing for what she had done. The two sisters later join the celebration in Ponyville, where Luna receives a welcome wreath in wonderment, and gazes up with an anxious smile at her older sister.

Excessive decorum
Princess Luna returned to the show exactly one year after the broadcast date of Friendship is Magic, part 2, in the episode Luna Eclipsed. The episode takes place in Ponyville during Nightmare Night. Despite wanting to win over the citizens of Ponyville, the townspeople are frightened of her booming voice and assertive manner. Twilight Sparkle tells Spike that Luna must be having trouble adjusting after being gone for a thousand years.

When Luna tries to express her happiness with being purged of her dark powers, Twilight tells her that she sounds like she's yelling, and Luna explains that she's using the "traditional Canterlot voice", the royal we, and high volume in order to properly address her subjects. She uses archaic terms like "hath," "thy," "nay," and "thou," as well as other constructs.

Twilight encourages Luna to lower the volume of her voice, but Luna is hesitant. Twilight Sparkle recruits Fluttershy's help in teaching Luna to speak in a softer voice, and later takes her to Ponyville so Applejack can show her how to be likable. For a short while, Luna manages to mingle with the villagers of Ponyville and have fun with them, by playing games where she throws toy spiders or pumpkins onto a target. In Sleepless in Ponyville she seems to show less of her former decorum, dispensing with the royal we, and speaking in a far less harsh manner.

Temper
Princess Luna reverts to her intimidating self after Pinkie Pie accuses her of eating Pipsqueak, while she was actually saving him from drowning in the apple bob. She attempts to endear herself to the villagers by turning toy spiders into real spiders, trying to elicit "fun" by making them crawl on their own to the bulls-eye, but the spiders only frighten everyone. The villagers panic and flee, and after a few seconds of indecision, Luna stops the commotion by shouting "BE STILL!!!" in her royal Canterlot voice, to the accompaniment of a crack of thunder. She then decrees in anger that since the ponies dishonor and insult her with the celebration, Nightmare Night is canceled forever.

Playfulness
Thanks to Pinkie Pie's insight, Twilight Sparkle realizes that because of the holiday, Pinkie Pie and her entourage actually want to be frightened, so she arranges for Luna to purposefully scare them. Luna appears as Nightmare Moon, scares the ponies, and bares fangs. After the ponies run away in fright, she changes back to her usual appearance and spits out the false fangs she was wearing, confused as to why Twilight wanted her to do that. Then Pipsqueak approaches Luna on behalf of the children and asks her to come back and scare them again next year, even though she canceled Nightmare Night. Luna begins to understand and reinstates Nightmare Night, at which point Pipsqueak declares her his "favorite princess ever" and hugs her leg.

The princess manages to relinquish the use of her royal Canterlot voice, and in the epilogue she plays a variety of games with the villagers, accepts the foals' candy, and frightens Rainbow Dash by firing a bolt of lightning behind her, a trick that Rainbow Dash had been playing on other ponies over the course of the night.

Kindness and wisdom
In the episode Sleepless in Ponyville, she displays kindness and offers wise advice to Scootaloo when she tells her to face her fears. At the end of the episode she gives Scootaloo a wink and a smile, as she knows that Scootaloo has faced her fears and she also knows that she has Rainbow Dash to help her overcome them.

In For Whom the Sweetie Belle Toils, Luna once again appears in a nightmare; this time, in Sweetie Belle's nightmare. She gives advice to Sweetie Belle and tells her that she as well has a sister that often "shines more brightly" than her and that she struggles with it. Then she takes Sweetie Belle into the past at her fifth birthday party, and shows her that Rarity did not want to take over the party, just simply save it. Later, Luna tells Sweetie to go inside a door of what the future might hold if she does not fix her sabotage of the headpiece Rarity had designed for Sapphire Shores. Later in the episode, Luna appears again in Canterlot, in order to help Sweetie Belle undo the damage she did to the headpiece.

Raising the moon
Princess Luna is said in the first episode to be responsible for raising the moon to bring about the night. When she refused to lower the moon to make way for the sun, her older sister Princess Celestia had to use the magic of the Elements of Harmony to stop her. Celestia was then responsible for raising and lowering both the sun and moon, while Luna was trapped in the moon for a thousand years.

In the episode Hearth's Warming Eve, Spike narrates that this magic is not exclusive to Luna and Celestia, but is or was performable by unicorns collectively.

Wielding the Elements of Harmony
In The Return of Harmony Part 1, Celestia mentions that she and her sister both wielded the Elements of Harmony to defeat Discord and turn him to stone. This is further shown in Princess Twilight Sparkle - Part 2 where it's revealed that she held the elements of Laughter, Honesty, and Loyalty specifically.

Weather manipulation
Nightmare Moon uses lightning to repel the guards in Friendship is Magic, part 2, and thickens the mist over the fallen bridge later in the episode to prevent Rainbow Dash from hearing Twilight Sparkle calling out to her.

Princess Luna manipulates the weather too, in Luna Eclipsed. She makes clouds swirl above her in the sky when she decrees that Nightmare Night is canceled, and produces lightning from a cloud to playfully frighten Rainbow Dash, who has been doing the same to other ponies throughout the episode.

Transformation
Nightmare Moon's mane is made of night blue mist bordered by translucent purple (Very similar to her design in Luna Eclipsed) that floats around without form. She can expand it at will, and apparently uses it as many extra limbs, using the tip of it to flick Rarity on the chin when intimidating the ponies in Ponyville. She holds the Elements in her hair while confronting Twilight before she is defeated. She also transforms into a sinister mist several times. She appears out of the mist in Ponyville's pavilion where the Summer Sun Celebration is being held, and she leaves the pavilion in a similar way, flying out into the night. The mist floats by Twilight's library window as the ponies learn that the Elements of Harmony are located in the "Ancient castle of the royal pony sisters"; it follows them throughout their journey.

When the ponies stand on a cliff side, the mist seeps into the ground, and the cliff side collapses as the mist leaves. The landslide carries the ponies to the mouth of a deep chasm, with Twilight Sparkle dangerously dangling over the edge, but Applejack keeps her from falling long enough so her Pegasus friends Fluttershy and Rainbow Dash can catch her and bring her down safely.

The mist floats straight into a manticore, making it lift its paw and growl. When the ponies come across it, it growls and attacks them, and the ponies fight back. Fluttershy manages to stop the fighting and calms the beast, then extracts a thorn from its paw, making it docile and affectionate. After the ponies leave, the thorn turns to purple mist.

The mist then seeps into several trees when the moon sets, and in the darkness the trees appear as monsters. All the ponies are frightened, except Pinkie Pie, who bursts into song and shows the other ponies that the monstrous trees turn back to normal when they laugh at them.

When the ponies come across a sea serpent, he tells them that a "tacky little cloud of purple smoke just whisked past [him] and tore half of [his] beloved mustache clean off." The serpent's agitated wiggling causes the river to be tumultuous, preventing the ponies from passing it. Rarity, deeply affected by this "crime against fabulosity", picks off a sharp scale from the serpent, cuts off the hair from her own tail, and magically restores the serpent's mustache with it. The calm, grateful serpent creates a bridge out of his own coils and helps the ponies cross the river.

The purple mist appears again, slithering past Rainbow Dash as she tries to fix the fallen bridge leading to the ancient castle ruins. Rainbow Dash hears someone calling her name, telling her they have been awaiting her, the "best flier in Equestria". "The Shadowbolts", a trio of ponies who resemble The Wonderbolts from Rainbow Dash's poster, gallop from the darkness and introduce themselves as "the greatest aerial team in the Everfree forest", then ask Rainbow Dash to join them as captain. When Rainbow Dash asks to fix the bridge first, the Shadowbolts present an ultimatum: "It's either them or us". Dash thanks them for the offer but declines, and fixes the bridge for her friends. The Shadowbolts then turn into the same starry purple mist, join together, and float away.

The purple mist appears one last time when the ponies find the Elements of Harmony. It swirls around the elements and teleports them, along with Twilight who jumps into the whirlwind, to another chamber in the ancient castle ruins. Nightmare Moon appears with the Elements floating around her, then she and Twilight charge each other; Twilight teleports to the elements midway, and Nightmare Moon turns back to mist and quickly floats back to the Elements. She shatters the elements by stomping on the ground, and declares that "the night will last forever." Twilight's friends join her, and after figuring out the magic of the elements, they transform Nightmare Moon back to her former self. Princess Celestia returns and reunites with her sister, offering her the chance to rule Equestria together once again.

Later in the series, in Luna Eclipsed, Luna transforms into her Nightmare Moon form with a set of false fangs, to playfully frighten some foals for Nightmare Night. In the same episode, she transforms objects instead of herself in one scene; specifically, toy spiders into living spiders.

Dream duty
Luna appears in the moon and in Scootaloo's dreams in the episode in Sleepless in Ponyville. She comes out of the circle of the moon and tells Scootaloo that "I am the princess of the night, thus it is my duty to come into your dreams." Scootaloo realizes she's dreaming and Luna tells her to face her fears. Scootaloo later sees Luna in the moon in the waking world, as a light purple silhouette with white, glowing eyes as she reminds the filly to face her fears.

Luna makes a similar appearance in Sweetie Belle's dreams in the episode For Whom the Sweetie Belle Toils. She shows Sweetie Belle visions of her past, the present, and Rarity's future. She also briefly appears before Sweetie Belle in the waking world, helping her fix the mess she made earlier in the episode.

Deleted scene
A scene with Rarity giving Princess Luna a makeover was cut from the episode Luna Eclipsed. The post-makeover pink Luna appears in a Flash asset of the game Castle Creator.

Royal guards
Princess Luna's royal guards look quite different from Princess Celestia's guards. They wear black and purple armor reminiscent of Nightmare Moon's armor. And most significantly, they have purple dragon or bat-like wings instead of the standard feathered Pegasus wings. They are grey-brown and have yellow eyes with pupils in the form of slits. Their ears appear to be furrier than normal. The carriage they pull is aggressive and Gothic, with streamlined shapes evoking bat or dragon-wings as well as arrow-like or spear-like accents. It is built with a low center of gravity, and Luna's royal guards pull it via heavy chains.

A Canterlot Wedding
Luna makes cameo appearances in A Canterlot Wedding - Part 1 and Part 2. In Part 1, Luna takes over the night shift from her sister after flying in silhouetted by the moon, and later tells Twilight to remain inside after spotting her running towards the castle. She appears again in the end of Part 2, when she flies in greeting everyone and asking if she missed anything. Luna dances with the other ponies after Pinkie Pie and DJ Pon-3 start the wedding party music which concludes the episode.

The Crystal Empire
Luna makes brief appearances in The Crystal Empire - Part 1 and Part 2. In the first part, she expresses doubt to Celestia over whether Twilight is ready for her task. She reappears at the end of Part 2. She and Celestia watch as Twilight and her friends return home. Luna then conjures up a spiral-bound book, as Celestia nods, confirming that her student is "one step closer to being ready."

Magical Mystery Cure
Luna appears near the end of Magical Mystery Cure alongside her sister and Princess Cadance, attending the coronation of Twilight Sparkle as a Princess. She can be seen wearing a dress and more ornate, elaborate versions of her crown, shoes, and collar. It is also revealed that the book Luna had produced at the end of part 2 of The Crystal Empire was the journal of Star Swirl the Bearded, which contained an unfinished spell that Celestia believed Twilight to be capable of completing.

Princess Twilight Sparkle
Luna makes appearances in Princess Twilight Sparkle - Part 1 and Part 2. In Part 1, while Princess Celestia speaks to Twilight about the Summer Sun Celebration, Luna is seen on a nearby castle balcony, happily raising the moon. During the episode, she is captured off-screen by black vines growing out of the Everfree Forest. Twilight and her friends free her and Celestia in Part 2 by giving up the Elements of Harmony to the Tree of Harmony. At the end of Part 2, Luna takes part in the Summer Sun Celebration, lowering the moon so Celestia could raise the sun.

Twilight's Kingdom
In Twilight's Kingdom - Part 1, Luna assists Celestia, Cadance and Twilight in welcoming the Duke and Duchess of Maretonia. Shortly after, Luna joins the two princesses in a song, admitting to Twilight that she understands how she is feeling. In Twilight's Kingdom - Part 2, she and the other princesses transfer their magic to Twilight; Luna's cutie mark—unlike those of Celestia, Cadance, and the ponies whose magic Lord Tirek steals—does not completely disappear, losing only the moon marking and retaining the darker part underneath.

Depiction in Equestria Girls
In Equestria, Luna tells Twilight that she only has three days before she'll be stuck in the alternate world for thirty moons, and that she must get back before the third moon reaches its peak. In the alternate world featured in My Little Pony Equestria Girls, the human Luna is the vice principal of Canterlot High School and her sister Celestia is the principal. The human Fluttershy brings Twilight's crown to her after it falls through the portal. She is later fooled by Sunset Shimmer into thinking Twilight destroyed the decorations for the Princess of the Fall Formal dance, until Flash Sentry provides evidence to the contrary. She holds the ballot box after the students finish fixing up the hall for the Fall Formal. At the dance, she carries both the envelope and the crown in a box to Celestia after Flash's band stops playing. She then hands the envelope to her sister to read who the Fall Formal Princess is. She is next seen being awoken from Sunset Shimmer's hypnosis alongside the students. Lastly, she is seen handing a trowel to the repentant Sunset Shimmer, so she can repair the damage she caused to the school.

Depiction in comics
Princess Luna appeared in one of the standard variant covers of the first issue, despite the fact that she makes no appearance in the story proper.

In the series' second four-part story arc, Nightmare Moon is shown to be a completely separate entity from Princess Luna. It is revealed that Nightmare Moon is a creature of darkness born on the moon whose very presence corrupts the denizens of the moon. Through her power over nightmares, Nightmare Moon was able to feed off Luna's insecurities of living in her sister's shadow, thus allowing her to take over Luna's mind, which ultimately lead to her being banished to the moon for a thousand years. Although the Elements of harmony were able to restore Luna back to her original form, Nightmare Moon herself continued to live on. Eventually, she hatched a plot to take on physical form by using one of the Element bearers, thus making the other five Elements of Harmony useless.

Just as she did with Luna, she begins invading the Element bearers' dreams until she is able to find a suitable candidate in Rarity, whom she abducts and takes to the moon. Princess Luna joins the other five Element bearers and Spike on a mission to retrieve Rarity before Nightmare Moon takes her over completely. However, Nightmare Moon's return seems to have weakened Luna as she is once again reverted to her "depowered" form (as seen at the end of "Friendship is Magic, part 2"). Upon arriving to the moon, they find that they are too late. Nightmare Moon has already taken over Rarity, and Luna is powerless to stop her in her weakened state, which forces her to retreat back to Equestria, leaving Spike and the remaining Element bearers behind. Back in Equestria, Luna helps Celestia and the residents of Ponyville defend themselves against the invasion Nightmare Moon and her minions.

Initially, Luna's magic proves to be just as ineffective as before, but through the love and support shown from her subjects she is able to regain her proper form and, with the help of the power of the other Element bearers' friendship, is able to best Nightmare Moon, save Rarity, and restore the denizens of the moon back to their original forms.

Princess Luna appears on page 7 of in Rarity's dream along with part of Hush Now Lullaby. She appears again in, participating in several Summer Wrap-Up Festival games with (an unwilling) Big McIntosh. In, towards the end of the festival, she is shown kissing Big Mac on the cheek as they ride the Ferris wheel. On page 5 of the story The Fall of Sunset Shimmer, a book titled Secrets of Nightmare Moon is visible on a shelf in a dark magic library in Canterlot Castle.

In  Luna thinks Celestia's job is much easier and takes over Celestia's work for a day. Luna realizes that her sister does do a lot of work and decides to go back to working solely during the night. Part of her nightly duties appears to be hunting and defeating monstrous beasts. In the issue, Luna also gets a pet opossum, which she names Tiberius.

Merchandise
The following were part of the Target Canterlot toyline:
 * Fashion Style Princess Luna was bundled with Celestia.
 * A Playful Ponies sized Luna was bundled with a molded Celestia.
 * A Shine Bright light-up Luna was bundled with the Canterlot Castle set.

Other merchandise include:
 * A Nightmare Moon figure which was released in the Toys 'R' Us exclusive Friendship Is Magic Favorite Collection, in Fall 2012.
 * Princess Luna being part of the Wave 5 mystery pack toys.
 * A newer Playful Ponies Princess Luna being released along with Rarity and accessories and it featured a newer model as apart of the Crystal Empire toyline.
 * A large talking Nightmare Moon was shown at the Toy Fair 2013. Yet to be released
 * A Design-a-Pony Princess Luna figure.
 * An Equestria Girls human doll of Luna came in the Pep Rally set with AppleJack, Rarity, Rainbow Dash, and Fluttershy.

My Little Pony mobile game description
''Formerly Nightmare Moon, Princess Luna is the younger sister of Princess Celestia. Ruling over the moon and the stars, Luna helps Celestia oversee Equestria.''

The Elements of Harmony guidebook
''Princess Celestia's younger sister, PRINCESS LUNA, has a history of difficulty living in her older sister's shadow. So difficult, in fact, her jealousy turned her into the villain Nightmare Moon! Fortunately, Luna was reformed and her heart softened by the ancient and powerful Elements of Harmony. Luna and Celestia have forgiven each other and are loving sisters once again, but Luna has trouble adjusting to modern Equestrian life after her thousand-year-long banishment in the moon. Still speaking with ancient formality and finding it hard to move beyond her once fearsome image, she may struggle, but her intentions are pure and she is certain to find the happiness she seeks one day soon.''

As Nightmare Moon
''NIGHTMARE MOON is the malevolent alter ego of Princess Luna. In the dark form of Nightmare Moon, Luna is consumed with spite and enjoys manipulating unwilling ponies to do her bidding. Imprisoned in the moon, Nightmare Moon became even more dangerous when she escaped.''

Quotes
"Remember this day, little ponies, for it was your last. From this moment forth, the night will last forever!"

- Friendship is Magic, part 1 (as Nightmare Moon)

"You're kidding. You're kidding, right?"

- Friendship is Magic, part 2 (as Nightmare Moon)

"I'm so sorry! I missed you so much, big sister!"

- Friendship is Magic, part 2

"Citizens of Ponyville! We have graced your tiny village with our presence so that you might behold the real princess of the night! A creature of nightmares no longer, but instead a pony who desires your love and admiration! Together we shall change this dreadful celebration into a bright and glorious feast!"

- Luna Eclipsed

"[booming voice] Change our approach?"

- Luna Eclipsed

"Fun? What is this 'fun' thou speakest of? Pray tell, what purpose do these serve?"

- Luna Eclipsed

"Ha ha! The fun has been doubled!"

- Luna Eclipsed

"'Tis a lie! Thy backside is whole and ungobbled, thou ungrateful whelp!"

- Luna Eclipsed

"Huzzah! How many points do I receive?"

- Luna Eclipsed

"Citizens of Ponyville, you have been wise to bring this candy to me! I am pleased with your offering! So pleased, I may eat it instead of eating you!"

- Pretending to be Nightmare Moon, from Luna Eclipsed

"Child. Art thou saying that thou... likest me to scare you?"

- Luna Eclipsed

"OH, MOST WONDERFUL OF...! I mean... Oh, most wonderful of nights."

- Luna Eclipsed

"Rest, my sister. As always, I will guard the night."

- A Canterlot Wedding - Part 1

"Who goes there? Stay indoors, Twilight Sparkle."

- A Canterlot Wedding - Part 1

"Hello, everypony! Did I miss anything?"

- A Canterlot Wedding - Part 2

"A warm welcome to you, Scootaloo."

- Sleepless in Ponyville

"I am the princess of the night, thus it is my duty to come into your dreams."

- Sleepless in Ponyville

"It is time to face your real fears, Scootaloo."

- Sleepless in Ponyville

"FACE YOUR FEARS!!!"

- Sleepless in Ponyville

"Not another step!"

- Princess Twilight Sparkle - Part 1

"There can only be one princess in Equestria! And that princess... will be me!"

- Princess Twilight Sparkle - Part 1

"Luna? I am Nightmare Moon! I have but one royal duty now... To destroy YOU!"

- Princess Twilight Sparkle - Part 2 (as Nightmare Moon)

"Six locks... Six keys..."

- Princess Twilight Sparkle - Part 2

"I understand what you're going through, Sweetie Belle. I, too, have a sister who often shines more brightly than me, and with this I have struggled."

- For Whom the Sweetie Belle Toils