Rarity's first chapter. The other girls get a Journey to the Center of the Mind, or some sort of fantastic element. Rarity gets plain, vanilla PSTD- and you get to experience her fear in first-person!
There is this one nightmare she ends up having that is particularly disturbing; Tom crashes into the boutique, bellowing for Rarity to marry him. Rarity begs him to stay away from her but suddenly a cockatrice pops out of one of the bouquets he's holding and turns her to stone. Rarity then stands there, terrified, helpless and immobile as a bunch of rock servants show up and force her into a wedding dress. Tom then excitedly declares that he and his "rock princess" will be together forever...whether she wants it or not. Not only is it scary, but it's also practically dripping with Marital Rape License implications.
Loneliness. Everything about her and everything she does is absolutely terrifying.
The Bad Future where Discord is the absolute master of the world. Let's just say that the dead rising from their graves to devour the living daily and the fact that he has magic users, even fillies mass executed are the least horrifying things his reign entails.
Discord basically turned the Mane Six into his version of the Nazgul, and is shown forcing all of them, but especially Twilight Sparkle and Rainbow Dash, to relive the moment of their utter damnation over and over again.
As suprising as it sounds, the audio adaptation is worse. The images, which pull no punches don't help one bit.
Applejack's reharmonization shows what happened to the ponies of Equestria when Discord took over and their PSTD afterward; some of it (like Dr. Whooves calling himself "Queen of Eagleland" and Photo Finnish streaking and eating her own dresses) are hilarious, but most aren't, like Apple Bloom being turned into a necropony, Diamond Tiara and Sweetie Belle being turned into dolls, Bon Bon being turned into her namesake as her best friend Lyra squeezes and tries to eat her, Derpy wishing death on her daughter, Dinky, Silver Spoon's father trying to kill her with an axe, Twist's limbs twisting wildly out of control, Prince Blueblood being turned into a living ice sculpture of a mare being chased around by a living sun that wants to rape her to death and Philomena being forced to rebirth herself repeatedly and then being reduced to ashes, placed in an urn and tossed into the deepest of the Gala's fountains. The following sums the whole sequence up perfectly;
And AJ knew, AJ KNEW, that this was only a TINY PORTION of every pony in Ponyville!
Rainbow slowly turning into...something in her "True Healing" chapter. Fluttershy and Pinkie stopped it in time, but still...
Fluttershy's transformation into a Nightmare Moon-esque monster, and Fluttercruel possibly dying immediately after. Even the author admits he went too far with this one.
Princess Gaia brainwashing the reader at the beginning of "Teacher Teacher". Made even worse by the fact she still acts like Fluttershy, which makes it much creepier.
We finally get a good look at the Ponyville Bedlam House Screwball stays at...just in time to see Princess Gaia Mind Rape most of them out of frustration. And then there's the pegasus who seems to regain her sanity, only to realize her wings have been chewed off.
Princess Gaia changing "Everfree" to "Everkind". It's like she's taking away their freedom, forcing them to live in her own world, whether they want it or not.
Luna outright exploding at Fluttershy and Fluttercruel for their crimes. Its pretty much Mind Rape.
And the published version was edited, the original was apparently a good bit worse!
Celestia making a full 180 after an entire chapter of "good cop" and doing just about the exact same thing Luna did (only goes more out of her way to comfort Fluttershy after the What the Hell, Hero? part is overwith), but this time without giving 'Shy the comfort of her alter ego. It was enough to make her stain the mental floorboards.
The worst part? Celestia admits that, had Fluttershy's magic not spared the foals, she would've flown into a berserker rage, ripped her soul out of her body and imprisoned it in the sun for a lifetime for every life she killed! Oh, and Fluttershy would've felt every second of it. It takes a lot to get Celestia truly enraged, but you won't like her when she is!
Nightmare Granfalloon deserves special mention for being completely Ax Crazy and scary as all get out. Some readers even admit that she gave them nightmares.
Nightmare Granfalloon: Anger is dead-dead-dead! Pinkamena is dead-dead-dead! Bad foalhood memories are dead-dead-dead! Now there's only happy thoughts!
A bit of Fridge Horror about that? Remember that Pinkie's foalhood memories are represented by a baby version of herself...
It's not as obvious as the Brave New World universe, but it's certainly pretty dark. Even with Princess Gaia leaving a lot more free will in the process—Applejack's suggestion that Gaia didn't take in the central POV universe—it's still very much an assault on agency and personality. May count as an Esoteric Happy Ending for others, though, depending on how much you count being foaled as Mind Rape, as it isshrinking the sum of all evils in Equestria.
When he was Discorded, Silver Tongue tried to kill his daughter Silver Spoon with an ax. Let's just say the Emergency Response Team was very fast.
The effects of Onyx Tiara being Discorded: everypony he touched (save for himself -- and yes, he tried) became a physical match for his beloved wife, whom he'd lost to mental instability. He proceeds to turn all of his servants into a harem of false Golden Tiaras, consummates with them -- and when his real wife shows up, mind cleared and willing to love him despite finding him surrounded by his clones? He dismisses her as a parody and drives her off in tears. As if we needed any more proof Discord is a Complete Monster...
And then when the Mane Six defeat Discord he awakens to find himself surrounded by his traumatized servants, one of them a horrified colt, and they all remember everything that happened. EVERYTHING.
Entropy. Just Entropy! The entire scene with her is just terrifying.
And if a certain Loose Canon story is to be believed, she can literally make it so you never even existed to begin with.
We see later in origin Discord's reign in all its horrifying glory, but one that stands out is his previously mentioned Flutterpony genocide. He made a public butterfly collection out of them.
Galaxy/Wind Whistle's (Celestia refuses to tell which) fate. Dear lord...
Made worse by the fact he morphs her body into his. And just imagine how Twilight feels hearing that the Discord she and her friends encountered was a spirit using a pony's body as a host!
Discord's treatment of Diamond Tiara. He alternates between abusing her verbally and just flat (mundane) out Mind Rape, stringing her along with enough praise to keep her listening to him. What makes this even more terrifying is this is how actual abusers behave!
And how can we forget the utterly charming dream dear Diamond Tiara has while sleeping in a Canterlot park? The one where she finds herself alongside thousands of other ponies—earth ponies, unicorns, pegasi, flutterponies, even sea ponies—pulling a massive chariot with a gigantic horned serpent in it whipping them all and laughing as he roars, "Cry Havoc!". Word of God is that the scene was based on a similar one from All Dogs Go to Heaven.
While Diamond Tiara is in Canterlot she runs into a rather...disturbing Stallion. Who tries to kidnap her and do Celestia knows what to her! The only thing we get about his plans is this:
Stallion: You'll make such a wonderful doll. Pretty, silent, and obedient. Don't worry. You'll be pretty forever. I'll wipe away all those painful and annoying memories. They'll be nothing except being a nice little doll for ponies to look at and play with.
Although things thankfully end well, in the Loose Canon story "Not One of his Kind", seeing Canon!Discord's version of Fluttercruel trapped in Limbo, covered in bloody scares and missing both her wings and almost all of her limbs was pretty unsettling.
The trailer for the audio version of "Reharmonized" manages to take the hilarious "Queen of Eagleland" speech and make it utterly terrifying.
In keeping with the tone of "Discorded', the trailer focuses on the darker parts of "Reharmonized", including, among other things, Loneliness' reveal, Angry Pie's rampage, Mitta being dragged back to Sunnyville at the end of the Gaia arc, Silver Ax's rant, and, of course, Discord.
Also during the Mind Games arc, we get another glimpse of the Epilogue timeline (or a similar enough one) via a nightmare shared by Rainbow Dash and Scootaloo. In it, Traitor Dash kills an adult Scootaloo (who's apparently a Rebel Leader), and Discord decides to "reward" her by creating a play about her victory, and having her attend every single performance. Oh, and a detail that shouldn't be overlooked—during the fight, Scootaloo runs Traitor Dash through, but she doesn't die because the Element of Chaos Discord gave her has taken the place of her heart.
"Different From Everypony Else" gives us a depiction of Discord's attack on the insane asylum outside of Ponyville. What he did to the ponies working there, who, despite Onyx's opinion and how Discord depicted the place, are pretty decent ponies, is just absolutely horrifying. And the scene ends with Discord holding down the character who's point of view we're seeing through and preparing to drill into his skull or something equally as horrifying we thankfully don't see (he didn't kill or seriously hurt the guy, but that doesn't change what happened!).
Discord: This will only hurt for a second! So be sure to struggle and squirm a whole lot!
Mind Games Part 8. Discord finally manages to break Diamond Tiara, and she breaks so hard that she goes Nightmare. She even gets a new Cutie Mark out of it: the Star of Chaos.
