Development and appearance
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. 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.
Depiction in the seriesPrincess 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 unicornpowers to raise the sun at dawn. The younger brought out the moon to begin the night." 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 Spikedismisses 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.[4
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.
In Season 5, Nightmare Moon makes a more prominent appreance. In Do Princesses Dream of Magic Sheep, Luna speaks with a small sphere of black smoke, calling it the Tantabus, and tells it that she's ready. As the Tantabus eclipses the sun, Luna suddenly transforms into Nightmare Moon. To combat this threat, the Mane Six channel the magic of Rainbow Power and fire upon Nightmare Moon with beams of multicolored light. Nightmare Moon appears to resist it at first, but when the Tantabus tears open a hole in reality and escapes, the Mane Six's magic successfully returns Princess Luna to normal. The Mane Six gather around the confused Luna for a group hug. Princess Luna wakes up in her bed, the entire experience having been a dream, but she expresses deep concern.
Later, The Tantabus invades other ponies dreams, and Luna tearfully reveals that she herself created the Tantabus to punish herself with nightmares after the suffering she inflicted as Nightmare Moon. Realizing that the Tantabus is feeding off of Luna's guilt, Twilight and her friends rally around her, telling her to forgive herself. With her friends' help, Luna finally moves on from her past. As the Tantabus loses its strength and shrinks in size, Luna draws it back into herself before it can escape the dream world. The next morning, the Mane Six wake up feeling well-rested. Luna, however, is fast asleep in the middle of the room, dreaming peacefully. The episode ends with Luna in a restful sleep on a bed of grass, surrounded by colorful flowers and a waterfall.
During the Season 5 finale, As a result of the timeline being altered again, the castle of the Two Sisters still stands, Nightmare Moon rules over Equestria, and Rarity and Rainbow Dash are her followers. Upon learning that Twilight has been traveling through time, Nightmare Moon demands to know the source of her time magic, intending to change history herself so that the Elements of Harmony are never discovered. She even takes Spike hostage to ensure Twilight's compliance. Twilight leads Nightmare Moon to the Cutie Map, but she catches her off-guard, rescues Spike, and uses Starlight's scroll to return to the past once again.
PersonalityMuch 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". 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. 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 Dashto 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.
Design and PowersNightmare 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.
Depiction in comicsIn 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.
Season 1Friendship is Magic, part 2
Hearth's Warming Eve
Season 4Princess Twilight Sparkle - Part 2
The Cutie Re-Mark