Don't forget the Wooden Mask Salespony. The way he appears out of thin air behind Herpy, that creepy-ass grin (which changes into a freaky angry face after her learns Daring put the mask on) and his cryptic phrases. Good thing he's an ally …or is he?
Possibly even creepier than the Wooden Mask itself is it's dialogue. Mention is made of it whispering it's corrupting influence into Daring's head shortly before she puts it on. The lack of capitalization in certain parts combined with a deliberate lack of punctuation and the Mask repeating itself gives the impression of the spirit of the mask being a breathless, greedy, nigh-schizophrenic monster.
the power the power the unending power it can be yours mine ours just put me on put me on step aside and put me on you fool and receive my majesty
The dragon cowered, terrified, as the demon advanced upon him. Nightmare Moon smirked. "So, you wish for the power of the evening's heaven, my reptilian friend? The power of the stars? My power?" she asked Inti as she trotted over to him. The dragon began shivering as she slowly approached. Nightmare Moon stopped in front of Inti, lowered her head to his ear and whispered to him in a voice that only they two could hear, a voice dripping with pure malice and colder than the depths of space itself: "Then you shall have it."
Daring-Do herself gets into quite a few dangerous situations, especially in "The Legacy of Nightmare Moon". *shudder* It's a good thing Herpy was there to save her when he did…
It's rather unsettling whenever Coco Pie switches over to her Chocolat' mode. At times, Chocolat' can come off as even more psychotic than Ahuizotl. Good thing she's one of the good mares? Right?
That gold thing called Koloktos. It's so bizarre looking; how is it able to walk around on two legs without falling over? It has many arms, but none of them are used for walking, instead for carrying swords. It's very creepy when you think about it.
At least Minotaurs use their tails as counterbalance.
Particularly when he finds out that Mrs. Hoovett betrayed him. The story had him waver from tragic figure and complete monster, but when he found out Mrs. Hoovett was keeping his daughter's fate a secret from him, he lost the last bit of his soul. Not only does he bake her to death in retaliation, but his plans for the ponies he now believed stole his daughter would make Mrs. Hoovett's fate look like a Mercy Kill. Fortunately, he is stopped before he could try.
In the movie adaptation of Staff of Star Swirl, after Lightning Kicker's disappearance has been noted by Daring, there's a completely soundless pause…and then this music starts playing. This particular snippet of the soundtrack can possibly be the closest one can come to the concept of panic being captured in music.
The fate of the big Hoofstapo goon when he gets caught in the airship propeller.
Despite the inherent silliness behind the idea, the filthy University fridge that Daring is stuffed into by Ahuizotl in Curse of the Yeti is actually made rather creepy by how outright terrified Daring is of the thing.
To bring the point home, he has a record collection filled with nothing but the sounds of ponies screaming. Hours and hours of nothing but Ponies screaming, and he enjoys it. That's nothing to say about the potential
This fact becomes even worse when Fridge Horror strikes: what did he do to get those sounds to put on the records in the first place?!
Another fun fact? Rumor is, he turns ponies into glue.
Actually, it's easy to misss, but the implication is that he uses only their hooves... Which is worse.
Krastos: "It's nothing that won't grow back... Eventually..."
He may have a a lot of funny moments, but he is still definitely creepy-possibly the worst thing about him is that, while he's on the loose, every time somepony dies, he absorbs their immortal soul, meaning he has total control over what happens to it. So what does he do? He places it in a dark dimension of his own creation, where it will be tortured for all eternity. What's even worse is that he plans each torture specifically to match each pony, giving them some sort of ironic torture based on their Cutie Mark, or just whatever their special talent is if they're a creature without a Cutie Mark, like a griffon. He comments that sometimes when he's bored, he brings popcorn to one of those dimensions at just sits there and laughs at the ponies being tormented.
Not to mention the courtyard of the castle-it's covered in spikes, and each one has a screaming head impaled upon it.
Think about this: At one point, he wears the Wooden Mask, and we all know what that did to Daring. But Krastos? He is so evil that he isn't affected at all.
The unnamed(?) Big Bad statue in Children of Primus.
There's a widely-circulating theory that this is why the book ultimately never made it to publication; this being allegedly was ultimately deemed too evil and frightening for the younger foals that the "Young Daring Do" series is written for, to such an extreme degree that reigning it in would have required a complete rewrite of the entire book. Given that one of his first acts is to rip off another statue's head, crush it with its face still frozen in an expression of terror, and toss it aside in contempt, the theory is generally considered pretty plausible.
The nature of these statues is mind-shatteringly weird. Not only do they walk on two legs, but it's heavily implied that, rather than being animated by magic, they're some sort of otherworldly living machine, with electricity in place of blood. And some of them have pieces hanging off them that correspond to no body part of any known creature and serve no apparent purpose. Some of them have windows in theit torsos, wheels attached in odd places, or other bizzarre anatomical flourishes. They're like Koloktos, but weirder.
The Redhorn Cult. An insane cult of ponies that worship an evil God and appease it by sacrificing foals.
Plus, they also resurrected Koloktos as a Minotaur-headed abomination that can breath fire. And it doesn't just stop there, there is the part where Koloktos uses its flames to incinerate the Redhorn Cult leader, Lord Bullrush, to death.
It doesn't help that the story described him as "…shrieking in unfathomable agony while the violet inferno engulfed him." Brrr…
The Changeling attack in Return of the Fire of Friendship. And our heroes just barely manage to prevent the invasions of Baltimare and Fillydelphia.
And when he is thwarted, he attempts to rewrite history so that Celestia and Luna never rise.
The Boarg. Holy clopping horseapples, the Boarg.
The Obsidian Sentinel features Star Shimmer's paintings. Some of them aren't too bad-heck, the ones she drew when Earth Song was alive were downright cheerful. But after his death…oh boy. Let's just say that the painting of the eye crying tears of blood was one of her tamer ones.
And of course, there's the title character. When inactive, it's just a huge, somewhat unsettling statue. When active, the eyes glow red and it becomes a relentless force of destruction, attacking characters with it's spear and plowing down anything in its path. The Reveal that it's a brainwashed Earth Song doesn't help. In fact, it's even creepier, considering Earth Song's personality in Star Shimmer's flashback.
Darkling Brighteye is very unsettling, and the fact that we know so little about what he is until the very end just makes things worse. True, he admits early on that he can't fight his way out of a wet paper bag, but he's still creepy as hell, and his lack of action ability does not hinder his plans.
His final scene is incredibly creepy, with everything from his attempts at getting Daring to back down, to his temporary ascension to divine power, to his Family-Unfriendly Death, sending shivers down most readers' spines, if not outright making them scream.
From the same book, the death of Marshal Goldstar.
Goldstar's murder of Whitefrock definitely qualifies. What makes it worse is that we get to see every detail. Every crunch, snap, and gurgle is portrayed vividly, all culminating in the removal of his viscera.
In Burning Heart, during Fuergott's Villain Song, attention is drawn to her face. Her powers over Tartarus's flames are causing the tears trickling from her eyes to boil on her face.
The Assembler. Dear Celestia, The Assembler. Just the thought of waking up with a missing body part is enough to keep you off sleep for quite a while.
It's an easily missed line, but we actually do: a bipedal demon. A soul-stealing, bipedal, nigh-unstoppable demon in an EU book littered with Continuity Porn? Only Krastos matches that description. (Unless they were foreshadowing the world-eater, who can also take on a bipedal form.)
Steam Whistle mentions earlier "projects" that weren't as successful. We never hear any details about them either, but, considering this is Steam Whistle we're talking about, that can't mean anything good.
Also of note is the Assembler's fan-made Leitmotif, The Factory: a sinister piano rhythm that blends perfectly with the very thundering sounds of machinery and industrial devices. With the addition of violin music towards the end, the song is enough to get anypony's heart pounding in fear.
The fate of the remaining members of the Colt of Smooze. In one particular prison, a security camera recorded the whole thing. We learn that the Assembler was pissed enough that it didn't bother with the anesthetic gas for the coltist (everypony else got a dose, though), and took him apart completely (not one or two limbs, it scrapped him whole) while he was alive and screaming for help. We're spared the details, but we do get to hear his last words.
Though there's another scary thought: it's implied that one of the Colt members not only survived the Assembler's attacks, but she managed to fight it off, at least, well enough to escape. Only one Colt member is implied to have that level of skill, and she was by far the most dangerous of them all.
Both Sweeney Trot and Steam Whistle used to be perfectly normal ponies. One became a murderous cannibal who baked ponies into cupcakes and the other became an insane golem maker who created an abomination that would give Krastos a run for his money. The thought that anypony could turn into such a monster when the right buttons are pushed is terrifying. Even more horrifying is that even Desert Rose isn't immune, considering the revelation about the Colt Leader.
The Hoof-Held Cannon, a miniaturized version of the cannons used in the Marksmare, intended to be carried and used by single living creatures. While the idea of such a weapon is formidable enough, Steam Whistle's diary claims that it shoots death, and has the ability to instantly kill anything.
Although, we later find out that by "anything", Steam meant "anything organic". Which, while it means that Claddie and the Marksmare are safe, it also means that the Assembler is immune to it as well.
The Assembler: "You cannot kill what was never alive"
Greyhoof's massacre of Steam Whistle's other assistants when he found out about the Cutie Mark Replicator. What's worse is that Steam Whistle decides to just use their corpses in his experiments.
But not before scaring Greyhoof out of his rampage. It may be just the fact Greyhoof's an Unreliable Narrator, but messing with the fabric of reality on a regular basis apparently gave him quite an intimidating presence.
"Get back to work. Now."
The Blank Village is scarier than ever. Originally, their behavior was borne of paranoia and fear against a Cutie Pox outbreak (to the point where they completely ignored non-Cutie Mark-based lifeforms), with only Starlet really being truly malevolent. Here, they fully embraced her "No freaks" policy, and had the place prepared against any sort of escape plan.
The Great-Grandfather Clock, another of Steam Whistle's creations, made during a brief period when he experimented with Space-Time. The Clock, when wound by someone it doesn't belong to, transports whoever wound it a certain amount of years into the past (approximately one year for each minute wound back). The number of years they would have lived in the present are then added onto the lifespan of the clock's owner. And wouldn't you know it, Tight Ship, the manager of the inn where the clock is located, didn't actually inherit the inn from his father and grandfather...
When Outback Jack bucks open the wall around the clock, to reveal that the wall is full of cogs and gears. The clock has somehow been growing into the walls.
After Outback Jack and Bravado, through great effort, remove the clock from the wall, thus technically "removing it" from the inn's possession, all those years that Tight Ship has been staying alive catch up with him in an instant. The text goes into delightfully morbid detail as to his mane falling out and his skin turning to dust over the course of half a minute.
You know it's bad when Steam Whistle himself ends up wondering in his audio diary why he even made that thing. He even intended to destroy it, but Tight Ship made off with it before he could.
The Soul Seal, one of his first inventions. In paper, it was supposed to prevent soul stealing by binding the subject's soul to it, thus preventing it from being taken by outside forces. In practice? Thisincludesdeath.
Last but not least, the Wandering Whistle. Claimed by Steam to be one of his finest works, the Whistle (fashioned after the Tinker's Cutie Mark) is able to call back the souls of the deceased or those who have had their souls taken by the demon- but only very specific souls, and only as ghosts. Daren, Desert Rose, and Starlight find it fairly quickly... only to bring the attention of not only the Assembler and his army, but also the Leader of the Colt of Smooze, seeking to resurrect her deceased followers.
The Assembler: Secondary target located. You cannot run from me this time, Waste of Flesh.
And when the demons she brought with her prove to be hesitant in going against The Assembler, she kills one in gory detail, and says to the others in that Faux Affably Evil tone "Please, I'd hate to have to do that again". The way she brutally slaughters a powerful demon as easily and casually as though she was checking her mail inspires them to fight their hardest.
Claddie's infamous outburst when he finds out about Sweetie Bottle. You'd think Claddie, the crazy golem with the goofy accent and hilariously short temper, couldn't possibly be scary. You'd be wrong.
The other faculty members wonder if Storm was only able to stand up to Claddie because he was too drugged out to realize how bad Claddie was. Storm insists he didn't take crap from Claddie before and then was no different.
Daring Do and the Universal Cracks is chock full of Nightmare Fuel.
The revelation that Steam Whistle had one more creation, hidden deep below his abandoned Laboratory: the Universal Chisel, which very slowly weakens the barriers between dimensions.Steam Whistle gave the idea up, believing that even the potential for help beyond the universe wasn't worth the risk.
The Leader of the former Colt of Smooze using the Chisel to break through the Realities to try to find an Alternate Smooze that can help her. Her monologue, about how the sheer number of potential alternate realities means that there might be a universe in which the Smooze succeeded in consuming everything is terrifying enough, much less the very idea of there being Multiple Smoozes.
The Bizarro Universe Ghoul Dachshund, who hails from the same universe as the Colt Leader. Bizarro!Ghoul has completely given in to hedonism from his substance abuse, and was a follower of the original Colt of Smooze. He gibbers constantly and talks to himself, like an even worse version of certain feral Diamond Dogs.
The Colt Leader's Fate Worse than Death: by channeling them through the Smooze-coated Universal Chisel, she attempts to consume all alternate realities until she finds the Smooze Universe. However, she severely overestimates her abilities to do so, and after her struggling to control it fails thanks to intervention from Sweetie Bottle and the ghosts of Charity and Applesack, combined with Daring kicking the Chisel from her hooves and into the Multiversal Vortex, she goes insane from the countless universes flowing through her head, until she is ripped apart, and her soul flung into the ether.
Just before that, Storm realizes that decking the Colt Leader was not the best idea, so he whips out the Hoof-Held Cannon he managed a work-around with and shoots the Colt Leader in the face, blowing a giant hole in her head... but by then she had been infused with Smooze, so all it does is get her to fill in the hole and give him an annoyed look before impaling him with a Smooze tentacle.
Some of the Alternate Universes seen are quite horrifying on their own.
The Bizarro Universe that the Colt Leader hails from is extremely twisted, almost as if Discord had been let loose upon it.
The universe where everypony, including Daring, have been assimilated and recycled into Soulless Soldiers by an Alternate Assembler.
The Assembler: "It's not enough. It will never be enough"
As comedic as the idea is, the Mirror Universe with an evil Daring is also very sinister.
The alternate Claddie in this universe is completely bucking crazy, and apparently wiped out several towns during one of his tantrums.
And yet, his fate at the hooves of the Colt Leader was still too brutal.
And yes, there is a universe where everything has been consumed by the Smooze. It's song is no longer "Nothing can stop the Smooze", but rather, "Nothing stopped the Smooze".
Though that pales compared to the Krastos Universe. Some of the faculty members considered thought it being destroyed by the Smooze universe would be considered a Mercy Kill.
Smooze Golems. That is all.
The Blank World. Where the plague had wiped out all of Pony- and Zebra-kind. The worst part is that it is implied to have started in the Blank Village, meaning Greyhoof was right.
From the Space World, the Shadavar. Psycho ponies who will rape you to death, eat your flesh, and sew your skin into clothing (and if you're really lucky, they'll do it in that order). Then there's the secret of planet Diomedes, "the secret that broke Herpington's brain."
Though it is never seen in the story proper, Tabula mentions the possibility of a certain theory regarding the multiverse- a "Dimensional Supercollapse", in which an entire parallel universe, and everything in it, is instantly and painfully destroyed, explodes, then reverses and implodes, reducing the universe to "a grouping of miscellaneous atoms about the size of a Bit."
As if the evil statue from the Children of Primus wasn't bad enough already, we're shown a universe where he succeeded in ressurecting his army and defeating Optimus Prime. His entire army Came Back Wrong, making them even more horrifying than they were before, but he doesn't even care, as it means they can't question his orders. With this army of zombie statues, he has waged a campaign of destruction across Equestria, starting by razing the entire city of Spurlin to the ground, leaving little more than a pile of rubble. There's a reason why this one is referred to as the Destroyed World.
It's also revealed that the substance he used in the ritual was the blood of a world-eating demon whose consciousness spans multiple bodies across the multiverse and who is devoted to wiping out all of existence. This is bad enough as a world-building detail, but this demon actually plays a part later in the story. The Moonless World is moonless because he ate the moon, leading to a tragic scene where Nightmare Moon, badly wounded, returns to her sister to beg for forgiveness... Only to finally collapse and die in Celestia's hooves when the core of the moon is reduced to what can no loner even qualify as dust. Let's recap, this thing killed Nightmare Moon and consumed the moon itself with no apparent effort. And when Celestia and Princess Cadance attempt to use the Elements of Harmony on it, the best they can do is to send it away rather than imprisoning it. Meaning it's on its way back. The ecological and magical havoc losing the moon caused was just gravy after that. To make things worse, because of its multiversal nature, the world-eater probably knows where our world is in every universe, and could very easily be coming for coming for all of them. This is pointed out in-story, and nopony has any ideas how to stop it, other than "keep using the Elements and hope he doesn't find a way to counteract them."
The world-eater may be worse than Krastos. Krastos is occasionally funny, but the world-eater gives no indication of feeling anything but hate and hunger. And while Krastos torments individuals, the world-eater deals in wholesale destruction and extinction, wiping out millions of lives at a time even with a near-miss. And when it speaks, it adresses Celestia as though she was barely worth its attention, and ignores Cadance completely. It considers alicorns barely on the level of mayflies, and Celestia's lifespan, which most of us would consider too vast to contemplate, is just a blink of an eye to this thing. And its particular brand of entropy-oriented nihilism is pretty unnerving.
World-eater: "Moons crumble. Suns fade. Only the void is infinite."
Purloined Stone opens shortly after Discord's defeat, and we learn what Discord did to Daring and several others (Trigger alert):
Daring was made to hate her siblings and she injured Darren severely.
Herpy was made to ape Sweeney Trot in mannerisms and nonchalance about the cupcake recipe—including taunts at Lightning Kicker.
Okpono is made into a dyed-in-the-wool, grade-A sadist.
Blinkamena Brown goes Ax-Crazy on anypony with the least trace of bay in their fur, mane, eyes, or accessories.
The description of some of Greyhoof's degenerate clones in Mirror Pond.
The way Greyhoof mutilates himself when he gets infected.
His breakdown as he swears vengeance on Daring.
Jacanar's rooms in Caverns of R'ni. Especially vault with the electric cage and the minotaur's head in a box.
A city of millions of ponies, almost completely depopulated within a couple weeks.
When Mareahnee's dark secret is revealed, the Fridge Horror of what would have happened to Haytrus, Daring, et al. if Okpono had gone with them into Mareahnee. There do not appear to be any zebra Roneigh, after all.
When Celestia hits Revenant!Rex with a Turn Undead, while Rex survives, half his face is melted off, revealing the skeleton underneath.
When Erebus and Zeb have stolen somepony's strength and courage, the pony grows translucent.
In Cloudfall Conspiracy, Serpentine's death. Her lover, Sterling Silver, doesn't approve of her wanting no part in his plan to discredit and eventually kill Masra, so what does he do when she tries to get out? Drowns her in a vat of molten silver. This is horrifying enough, to say the least of when the university staff come out to the quad to find the new silver statue that has just been delivered to them...
In the Short Story Afterwards, we see the Afterlife that is waiting for Ahuizotl upon his eventual (and final) death: tormented by the souls of all the ponies he has wronged, for all eternity.
For one of the very few times in his life, Ahuizotl felt a certain emotion that he was not a particular fan of: fear. His jaw hung open at the black figure before him, his face all too familiar. Blackmane leaned down into Ahuizotl's face and whispered three words.
Taube's Raubvogel "bodysuit" in Breathing Weapons. To put it simply, her feathers and skin have been replaced with super-strong metal and electro-stimulators adhered directly to her muscles, amplifying her strength and pain tolerance.
Her mental state isn't pretty either. Her mind has been practically wiped, and she's now under complete control of Krahe. What's even worse, when she does show signs of resistance, Krahe gives her a painful shock to keep her in line.
Watching Eichelhäher succumb to the degeneration of her own mind and becoming a mindless, snarling ghoul is pretty unnerving.
The first time Eichelhäher discards her coat, revealing her rotting, decaying body (which is described in graphic detail). There's even a scene where her organs fall out. She just pops them right back in like it's nothing.
Henne herself isn't scary. The fact that such a sweet and caring woman is associated with a group of psychopaths like the Greifvögel, keeping up the warm, grandmotherly personality while her friends commit horrible, unethical acts to innocent griffons is horrifying.
Kind of softened later on in the story. (see below)
The scene where Eule cuts the wings off one of the failed experiments to give to Rabe. Made even worse when it's revealed it was still alive.
How about the reveal that all of the Greifvogel were all once just normal, good-hearted griffons who were kidnapped by Krahe and subjected to his horrible experiments?
Even worse, it's heavily implied that Rabe, his brother, was also heavily experimented on.
In Crown of Ulima Mule, the creepy, evil miasma that keeps muttering "crystalsss".
In Crimson, Black, and Blue; pretty much everything Black Bloom does. He's only a child, yet he manages to steal a powerful, mystical artifact from his king's castle and use it to steal years from three dragons, effectively cursing them to be children forever.
After losing the duel with Daring, he loses all sense and summons a meteor to destroy the kingdom, "If I can't have it, NO ONE CAN!!!"
Jackhammer's fate in Iron Grinder. It's heavily implied that he's left to die in the caves, pinned under a rock until he starves.
Greyhound Grave's hood. It's made from the head of a monster he slaughtered, with the mouth serving as the seeing hole, despite having multiple stitches on it.
A short excerpt from Music of Endings describes exactly what happens to Daring Do when she hears the eerie music. It describes her feeling somewhat tingly, the effects getting worse and worse until she's shivering on the ground in pain, feeling violently ill, and crying.
Fans were excited to see the Greifvögel make a return in Chemical Sister. What they didn't expect was them being little more than mindless zombies being used as tools for the military. Imagine Eichelhäher's situation, then make it ten times worse.
Eichelhäher before she gets her protective bodysuit. Her organs continue to fall out, and now her limbs have started falling off, forcing her to literally sew them back on.
Gospel really wanted to hammer in the "rotting body" details. Eichelhäher's brain is exposed at one point.
Krähe's fate. He's been ressurected by Fischadler (the titular "Chemical Sister"), and is used to grow and harvest various organs and body parts he grows. It's unknown whether he's conscious through this or practically brain-dead like the rest of the ressurected Greifvogel members. In a way, it just makes it more horrifying.
When Daring questions why Eule and Henne are with the rest of the ressurected (it was revealed in a previous story that the two were admitted to a mental health facility to undo the damage Krähe had done to them.) Readers are then treated to a flash back in which Papagei breaks in to the hospital they where in, leading to both of them having horrifying panic attacks before he straight up murders them and has Fischadler ressurect them as brain-dead bio-weapons.
Know what's worse? The story was based on a real case! Who knows where the Amulet is now. This tropony hopes it was destroyed...
In Marks of Destiny, earth pony Lemon Meringue's increasingly desperate attempts to master the weather duties that came with Dizzy Cloud's cutie mark.
The new trailer for Alicorn's Shadow scared the hay out of several people.
Mareton:(with a Slasher Smile)You wanna know how I got these scars? My father was an explorer, too, and we were fiercely competitive. And one time while we were exploring, he goes off crazier than usual. I grab a knife to defend myself…and he doesn't like that. Not one bit. So he takes the knife from me, laughing . He comes at me, shouting , "WHY SO SERIOUS?!" You wanna have scars to?!!''
There's something evil in that part of Everfree where Gusty Lulamoon's grim town's supposed to be. She died in that section, too; perhaps too much she knew?