A thousand years ago, Princess Celestia banished her sister to the moon, that much we know. What wasn't known, and what Celestia kept secret was that before her banishment, Luna had given birth to a foal. Now a thousand years later, as Nightmare Moon returns, Twilight Sparkle is going to find out exactly what it means to be the Heir of the Nightmare.
The establishment of the Eternal Night is upon Equestria. Old secrets long buried shall finally resurface, as Nightmare Moon shall crown her daughter Princess of Equestria. But why? What shadows lurk beneath the madness? And how shall Twilight Sparkle save Equestria from the wrath of her own mother?
Heir of The Nightmare provides examples of:
- Anti-Villain: Luna acts as Nightmare Moon were done because she felt only by becoming a feared tyrant, could she truly protect Twilight.
- The Night Guard are not mindless Mooks. They serve Luna out of loyalty for having protected them from the superstition and racism of the past, and thus they treat Twilight with absolute reverence. They do act very nasty toward the Mane 6, Shining Armor, and Cadence, but only because they see them as threats to Nightmare Moon, and are pretty nice to the other servants.
- Asshole Victim: Moloch and the Knights of Ra.
- Bond One-Liner: After Moloch is burnt alive, Luna utters, "So ends the Knights of Ra."
- Calling the Old Woman Out: When Nightmare Moon attempts to justify her actions as being done to protect Twilight, Twilight retorts that her actions have caused unnecessary suffering to ponies that have done nothing to hurt her. Nightmare Moon doesn't take it well, to put it mildly.
- Cassandra Truth: Cadence, Shining Armor, and Spike don't believe Twilight when she claims to be Nightmare's daughter, and think that she must have been brainwashed.
- Curbstomp Battle: Nightmare Moon is easily able to defeat the Mane 6 when the Elements of Harmony fail. In one day, the Royal Guard across Equestria capitulated to the Lunar Pegasi. It's justified because the Lunar Pegasi had been planning this for a millennium, and two of the Royal Guards were demoralized by Celestia's defeat.
- Eye Scream: In desperation, Fluttershy uses The Stare on Nightmare Moon. It almost works, but Nightmare resists and knocks her out cold. What is her solution to getting rid of The Stare? Severing Fluttershy's optic nerves.
- Fantastic Racism: The Lunar Pegasi suffered terrible discrimination in ancient times, because they were believed to have been spawns of dark magic. Regular pegasi would even throw foals off clouds for fun and of course, the Knights of Ra would sacrifice them. Luna offered them sanctuary in exchange for servitude, but after her banishment, they went back into hiding.
- Hoist by His Own Petard / Karmic Death: Moloch tried to cook Twilight alive as a tribute to Princess Celestia. In a last-ditch effort to kill Luna, he attempts a fire spell, only to have done it on a bundle of oily sticks. He is promptly burnt alive.
- Ironic Nursery Rhyme: Nightmare Moon sings "Twinkle, Twinkle, Little Star as she dementedly and viciously chases after her daughter Twilight.Twinkle, Twinkle, little star. How I wonder where you are. Up above the world so high, like a diamond in the sky. Twinkle, Twinkle, little star. How I wonder where you are...
- Knight Templar Parent: Luna became Nightmare Moon after her daughter Twilight was nearly killed by the Knights of Ra. The dark forces that were influencing her played on her fears, and convinced her that to better protect Twilight, she needed to make ponies fear her, and she could only do so by casting down Celestia, removing the sun, and taking over Equestria as a cruel tyrant. Nightmare Moon slams Cadence against a wall and if not for Twilight's intervention, would have broken her legs for yelling at Twilight.
- Morality Pet: Nightmare Moon is a merciless tyrant, but she does deeply care for Twilight. It disturbs Twilight that Nightmare can go from angry and vengeful with the object of ire, to peaceful and loving with her. Twilight eventually can no longer stand her brutality, and is forced to destroy her.
- Noble Top Enforcer: Noctis. While he does serve Nightmare Moon and mistreats Five of the Main Six, he only does so on the orders of Nightmare Moon, who he has pledged to serve for protecting his fellow Pegasi. He is horrified by Nova's destruction of Ponyville and her utter cruelty. When he realizes the Mane 5 are not remotely as dangerous as Nightmare Moon claimed to be, and pitying the loss of their families, he lets them go.
- Religion of Evil: Luna and Celestia never appreciated zealots who would treat them as gods, so they outlawed any worship of them. The Knights of Ra, a group of sun worshipers confirm their fears: they apparently sacrifice Lunar pegasi, collectively rail against Luna and the night, and were very eager to burn foal Twilight alive.
- Replacement Scrappy: In-universe, Nightmare Moon sees Cadence as this for Twilight, angry that Celestia couldn't at least raise Twilight, her own niece, to be royalty while giving Cadence, somepony not even related, that honor.
- Villainous Breakdown: Nightmare Moon suffers a particularly terrifying one after Twilight calls Celestia more of a mother than her. Her fury ends up wrecking the castle, and while chasing Twilight, she speaks in a particularly deranged voice, all while imagining her chase as a form of hide and seek.
- Villainous Valor: Even after his Knights had been killed by Luna, Moloch still made an attempt to kill her.
- What the Hell, Hero?: Cadence blows up at Twilight for letting her newfound motherly attachment to Nightmare Moon allow her to forget that her Eternal Night will kill the world, her humiliation and enslavement of Shining Armor and Cadence, and for possibly killing Celestia. Unfortunately for Cadence, Nightmare Moon overheard her yelling at her daughter.