Princess Luna

Princess Luna, known as Nightmare Moon (or Night Mare Moon) when transformed by the Nightmare forces or under certain other circumstances, is an Alicorn pony, the younger sister of Princess Celestia, and the main antagonist of the season one premiere of My Little Pony Friendship is Magic as Nightmare Moon. She is also the adoptive aunt of Princess Cadance. Eventually, the Elements of Harmony restore Luna to her former self and she returns to rule over Equestria alongside her older sister. Princess Luna/Nightmare Moon is called by her respective early names Princess Selena/Night Mare in another depiction.

Development and design
The word "Luna" means "moon" in Italian and Spanish, in both cases derived from Latin—Luna is the Latin name for the Greek moon goddess Selene (Σελήνη), 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. The Elements of Harmony guidebook states that Luna's original name was Selena and shows development and concept art of the then-named "Princess Selena"/"Night Mare"; these names are used in a Friendship is Magic storybook. According to Lauren Faust, Princess Luna's name "was Selena for a short time, but there were legal problems with it," and Nightmare Moon was originally named "Discord," a name which would later be given to another eventually-reformed villain.

Princess Luna's appearance changed in subsequent appearances after Friendship is Magic, part 1, with the exception of most of Nightmare Rarity (story arc). Her coat 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 some merchandise and the online game Castle Creator, 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 mane was then magical and wavy again because her good powers had been restored.

Luna's design is similar to those of Fleur Dis Lee, Princess Cadance, the Headless Horse, the Mane-iac, and S05 Unknown Unicorn Mare #8.

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 [the Mare in the Moon's] escape, and she will bring about nighttime eternal," though Spike dismisses it as "an old ponies' tale." While Twilight composes 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 tells Twilight that she "must 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 deeper detail. In a flashback, Twilight is shown the inciting argument between Princess Luna and Celestia, Luna stating she refuses 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 background 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. This 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.

Luna Eclipsed
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.

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 online game Castle Creator.

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. When Twilight drinks a potion given to her by Zecora, she is transported into a castle, where she encounters Luna. Luna proclaims that she will be the only princess in Equestria, and she undergoes a transformation into Nightmare Moon, much to Twilight's horror.

In Part 2, Celestia arrives to the scene, and an aerial fight ensues. Twilight soon realizes that the potion has taken her to the past, and that she is witnessing the banishment of Nightmare Moon. Moments later, Celestia uses the Elements of Harmony to banish Luna to the moon. Twilight drinks the potion again and witnesses Luna and Celestia battling Discord and turning him to stone for the first time. She also sees the two sisters taking the Elements from the Tree of Harmony. Later, 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 Celestia and Cadance in a song, admitting to Twilight that she understands how she is feeling. Later in the evening, Luna rushes into Celestia's room when she hears her scream from having a nightmare. She informs Celestia that she did not have a dream, but rather a vision. The next morning, she and Celestia tell Twilight the story of Tirek and his brother Scorpan, and how Tirek was imprisoned in Tartarus. Luna mentions that they believe Tirek escaped during the events of It's About Time when Cerberus left his post and attacked Ponyville.

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 Tirek steals—does not completely disappear, losing only the moon marking and retaining the darker part underneath. Tirek and Discord eventually break into Canterlot Castle and Tirek attempts to steal the three princesses' magic, but soon learns that they have transferred it all to Twilight. Luna, along with Cadance and Celestia, is sent to Tartarus as revenge for Tirek's original imprisonment. After Tirek is defeated, the three princesses are released and return home to Equestria.

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." She is portrayed as vicious and maniacal, shown when she attacks Princess Celestia and cackles evilly in Princess Twilight Sparkle - Part 2.

Bitterness
The narration at the beginning of Friendship is Magic, part 1 speaks of Luna'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. She then 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 stated in the first episode to be responsible for raising the moon to bring about the night. Following her imprisonment in the moon, Luna resumes this responsibility, as shown in Princess Twilight Sparkle - Part 1.

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. In Twilight's Kingdom - Part 2, Luna temporarily transfers her ability to control the moon, including all of her magic, to Twilight Sparkle.

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 Luna held the elements of laughter, honesty, and loyalty specifically.

Weather manipulation
Nightmare Moon uses lightning to repel the royal 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.

In Luna Eclipsed, Princess Luna makes clouds swirl above her in the sky when she decrees that Nightmare Night is canceled, and she produces lightning from a cloud to playfully frighten Rainbow Dash.

Transformation
Nightmare Moon employs powerful magic in addition to those stated above. She can expand her translucent, formless mane and use it as extra limbs, demonstrated when she flicks Rarity on the chin when intimidating the ponies in Ponyville and holds the Elements of Harmony in her mane while confronting Twilight.

On multiple occasions, Nightmare Moon turns her entire form into mist. She appears in this manner in Ponyville's pavilion where the Summer Sun Celebration is being held, and she follows the Mane Six on their journey for the Elements this way. While in this form, Nightmare Moon can manipulate creatures and environments.

In Luna Eclipsed, Luna transforms into her Nightmare Moon form with a set of false fangs to playfully frighten some foals on Nightmare Night. In the same episode, she transforms toy spiders into living spiders.

Dream duty
In Sleepless in Ponyville, Luna appears in Scootaloo's dreams, stating that as the princess of the night, it is "[her] duty to come into [ponies'] dreams," and offers Scootaloo guidance in facing her fears.

Luna makes a similar appearance in Sweetie Belle's dreams in For Whom the Sweetie Belle Toils and shows Sweetie Belle visions of her past, the present, and Rarity's future.

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.

My Little Pony 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 and Celestia. Lastly, she is seen handing a trowel to the repentant Sunset Shimmer so she can repair the damage she caused to the school with Snips and Snails.

Equestria Girls: Rainbow Rocks
In the sequel, Vice Principal Luna is seen accompanying her sister when they oversee the students working on signs and posters for Canterlot High's musical showcase. She is later heard calling Sunset Shimmer into the foyer since Sunset volunteered to show three new students around CHS.

The Rainbooms try to warn Celestia and Luna about the Dazzlings, but they are already hypnotized by the sirens' song. The principals later serve as the judges for the Battle of the Bands. After the semifinals, the Dazzlings hypnotize them and coerce their decision in favor of the Rainbooms instead of Trixie and the Illusions.

Perfect Day For Fun!
In the animated short Perfect Day For Fun!, Vice Principal Luna watches the Rainbooms' concert and poses for a smartphone photo.

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. When Sunset Shimmer says to Celestia, "This is the biggest mistake you'll make in your entire life," Celestia looks at a portrait of her banishing Luna and says "One of many." Of, Luna appears in PTV and is featured on a comic book in 1 million cover A.

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.

"explores the secret origins of" Nightmare Moon.

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 a part of the Crystal Empire toyline.
 * A large talking Nightmare Moon was shown at the Toy Fair 2013.
 * 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.

Other depictions
She appears in the Friendship is Magic storybook adaptation of the episodes Friendship is Magic, part 1 and Friendship is Magic, part 2, which is included in the Friendship is Magic Gift Set and Pony Friends Forever Pony Scooter Friends Daisy Dreams & Rarity bundles. Here, she is called by her early names "Princess Selena" and "Night Mare," and she does not physically appear in the Castle of the Two Sisters.

HubNetwork.com description
''Princess Luna raises the moon at night and rules Equestria with her big sister, Princess Celestia, who's also an Alicorn. Luna was banished as Night Mare Moon for a thousand years, but with help from Twilight Sparkle and friends, she's back. Her formal speech may still frighten ponies, but she's beloved by everypony and celebrated on Night Mare Night [sic]. On occasion, she appears in ponies' dreams.''

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.''

The Journal of the Two Sisters
In The Journal of the Two Sisters, Luna at first writes her journal entry in the royal Canterlot voice, but then decides against it. She reveals that she and Celestia used to speak that way when they were younger and pretended they were princesses. It is also revealed that even when they got their crowns, the sisters were still blank flanks, due to Alicorns aging differently from other ponies. When Luna speaks to a Manticore named Melvin, it is revealed that she is able to understand the language of certain animals, like Fluttershy does.

Luna befriends cragadiles, bats, and owls, who help with the construction of the Castle of the Two Sisters, and the zebras, whose rhyming way of talking plays into her and Celestia negotiating a new peace treaty with Gregor and the griffons. Luna also becomes very good friends with Princess Platinum after she apologizes and even promises to teach her how to do the royal Canterlot voice.

Luna bears witness to one of the few times Celestia is pushed to the point of using her own royal Canterlot voice to subdue a creature that has severely disrespected and angered her when retrieving the Crystal Heart for unicorn Princess Amore, then-ruler of the Crystal Empire. When a dragon claims the Crystal Heart as his property since it was mined from his keep, Celestia lashes out in righteous fury at him, scaring him into returning the Heart and flee to his keep, never to be heard from again.

When Star Swirl the Bearded reveals his unicorn magic has been exhausted attempting to lower the moon alone without the assistance of several other full-grown unicorns, he asks Luna and Celestia to do it as their Alicorn magic is more powerful, and doing so could actually revitalize them. The princesses lower the moon and raise the sun flawlessly, and they earn their cutie marks at long last.

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

"So, to be funny I have to torment those who oppose me and laugh in their faces?"

- page 12

"Soy la princesa Luna, y gobierno Equestria junto con mi hermana mayor Celestia, ahora que he vencido a mi lado malo, Luna de Pesadilla, ¡qué mal lo hemos pasado! Estuve 1000 años en la luna, pero ahora he regresado y me encargo de hacer anochecer. Me encanta hacer que los sueños de todos los ponis sean preciosos."

- Promotional image