The Stars Will Aid Their Escape is a crossover fic of My Little Pony: Friendship Is Magic and the Cthulhu Mythos. After being driven out of Ponyville following the incident with the Ursa, Trixie flees into the Everfree forest, where she meets a mysterious masked stallion named Herald.Herald offers Trixie a chance to learn ancient magic that will truly make her the most powerful unicorn in Equestria, by offering her a book that not even Twilight Sparkle has ever read. But there is a reason Twilight's never read this book, and there is more to Herald than there appears...Can be read here.
Bigger Bad: The Outer Gods. Reinforced when even after the Bearers temporarily defeat Herald by sending him where he sent the Princesses to fight them, they then have to deal with the pending arrival of Shub-Niggurath. And then, when she's banished without fully emerging, they then have to fight off Nyarlathotep again.
Big Damn Heroes: Princess Luna and a couple of her royal guards show up just in time to save the Mane Cast from Trixie and her Dark Young mooks.
When Nyarlathotep throws the jar containing the Cutie Mark Crusaders' souls over the Canterlot waterfall, Rarity dives after it to save them, and is then saved herself by Rainbow Dash.
Also tries it with Celestia and the other Element Bearers (and seems to succeed with Pinkie).
Everyone recovers by the time everything's done with.
Brown Note: The Red Sigil (an obvious expy of the Mythos' Yellow Sign) that Trixie casts during the attack on Canterlot causes anyone who glimpses it pain, and directly looking at it drives you insane.
Seeing what Herald looks like under his mask has a similar effect, minus the pain part, since it seems it forces knowledge of the Outer Gods into the viewer's mind. This is what he does to Twilight.
The Cavalry Arrives Late: Shining Armor gathers as many Royal Guards as he can to fight Herald during the attack on Canterlot... only to find that the Bearers have already managed to send him to the place he sent the Princesses with Spike's fire breath.
The Chessmaster: From the minute he showed up, Herald had everything going the way he wants. He actually uses chess metaphors a couple of times.
Cool Mask: Herald wears one — which is a good thing, because seeing his true face drives the viewer insane. Which is what he does to Twilight.
Curb-Stomp Battle: Nyarlathotep manages to defeat the Princesses quite easily when they're weakened by the eclipse. Shortly after, he's attacked by all the Element Bearers (and Spike) at once, and swats them all away with one hoof.
The Princesses return the favor outside of reality. While Nyarlathotep can fight back, they still are pounding him so badly his Healing Factor can't keep up and he's ultimately forced to flee back to reality.
Of course, then Twilight recovers and together, the Bearers return the favor when banishing him back where he came from.
Dangerously Genre Savvy: Herald, aside from manipulating the entire story to his favor, also admits that the Elements of Harmony might actually work on him, and so states that he will kill the Bearers if they so much as try to use them.
Backfires on him in the end when he assumes the fear of him killing them will prevent them from using them. When their bond to each other proves stronger than their fear, he's left open to a point blank blast of the Elements of Harmony.
Didn't See That Coming: Herald assumed the fear of him killing them would be enough to stop the Bearers from using the Elements against him and thus is left open when they overcome said fear and blast him point blank, and apparently didn't realize emerging into reality right in front of them would give them the opening they needed to do so.
Earlier than that, and the point where his entire plan starts falling apart, he didn't expect that one of the mane six would think to use Spike to send him outside of reality to face the Princesses. They not only manage to begin winning against him, but this buys the mane six enough time to kill the Dark Young and foil his attempt to summon Shub-Niggurath.
Did You Just Punch Out Cthulhu?: Well, not Cthulhu, he doesn't even appear, but the mane six manage to defeat Nyarlathotep with the Elements of Harmony. They also kill the Dark Young and manage to banish Shub-Niggurath back where she came from, but they didn't actually fight her.
Do Not Go Gentle: Twilight decides that if using the Elements on Herald gets them killed, then at least they died together, defending her people and her world. Considering Herald was banking on the fact they'd be too afraid of him killing them if they tried to use the Elements on him, it doesn't end well for him.
Driven to Madness: Trixie is left completely insane from just one use of the Neighcronomicon and a little prodding from Herald. She's so out of touch with reality that she views the Dark Young as trees she's animated.
When Herald identifies Twilight as a threat, he shows her his face, which leaves her a screaming, incoherent wreck that has to be restrained and repeatedly sedated.
She gets better (somewhat) with help from Luna.
Happens to a great many ponies when Shub-Niggurath starts emerging.
Eldritch Abomination: Obviously, though so far we've only seen the Dark Young (which are low-level enough that while the ponies view them as wrong, they're not mind-breakingly wrong note except in Trixie's case, but that was mostly Herald's doing) and Herald (who is Nyarlathotep disguised as a pony).
Shub-Niggurath starts to emerge during the Eclipse, during which the stars are blotted out and the sky is filled with mouths.
Empty Shell: The Cutie Mark Crusaders, after Herald rips their souls out. They get better at the end.
Enemy to All Living Things: All of the Mane Cast's pets are afraid of Herald on sight, Winona is too scared to follow his scent, and he's even able to cow Timber Wolves to his bidding (which is how he orchestrates his first meeting with Trixie).
Equine Resources: Nyarlathotep offhandedly mentions at one point that the pages of the Neighcronomicon are bound in the flesh of its author.
False Reassurance: When Trixie asks whether the Neighcronomicon is bound with leather, the Herald tells her that it isn't bound with cow hide.
A Form You Are Comfortable With: Herald looks like an ordinary stallion, but is actually an Eldritch Abomination in pony form (Nyarlathotep, in fact). This carries over to a cutie mark that seems to constantly be changing form (though it's hard to see on his dark coat, and trying only gives you a headache), and the fact that if you see him without his mask on, you go insane (which he inflicts on Twilight).
It's also implied that the princesses do this as well, as when they fight Nyarlathotep outside reality, they take on forms of pure power that no pony would recognize as them.
A God Am I: Herald starts indulging in this after outing himself as Nyarlathotep. Admittedly, he is, but still...
Godzilla Threshold: The last time Nyarlathotep emerged into Equestria, Celestia had to call down the power of the sun to destroy him, obliterating everything for miles in the process. He describes it as having been inconvenient.
Heroic BSOD: Fluttershy, when she realizes that not only does her ability to communicate with and calm down living things not work with the Dark Young, but that they're not angry or misunderstood — they are actively malicious, and they want to hurt her and the others.
Spike, following Twilight being rendered insane.
Applejack, Rarity, and Rainbow Dash, after the Cutie Mark Crusaders are hospitalized. Dash's case is the worst, since Herald manipulated her into thinking it's her fault.
Pinkie slips into one Nyarlathotep reveals that he's stolen the Cutie Mark Crusaders souls. Rarity is bordering on herself at the same time.
Hoist by His Own Petard: For all his Genre Savvy, Herald ends up being defeated by several of his own actions throughout the story. Throwing the CMC's souls over the waterfall not only allows them to be retrieved, but takes away the one thing that might have stopped Pinkie Pie from banishing him to outside of reality the same way he did it to the Princesses. That action in and of itself ends up costing him, as it allows them to fight him at full strength without having to worry about hurting their subjects as they would in Equestria, allowing them to begin winning the fight. This also buys the mane six enough time to kill the Dark Young and stop Shub-Niggurath's summoning.
Hope Spot: Subverted. After Shub-Niggurath is banished, Nyarlathotep in his true form returns to try and kill them all. The Element Bearers respond by blasting him back where he came from.
I Am Not Left-Handed: Herald finds out the hard way that the Princesses generally hold back when there's innocent bystanders to hurt. Once he's banished outside reality, even going One-Winged Angel isn't enough to stop them from using their full power and teamwork to kick his flank.
I Have Many Names: He doesn't say it himself, but when Twilight is reading the vague reports on Herald/Nyarlathotep, she comments that he/it is referred to by multiple titles.
Lack of Empathy: Herald states that this is why Fluttershy's instinctive ability with animals and the Stare don't work on him or the Dark Young — they have no sense of compassion or remorse for her to tap into.
Look, a Distraction!: Twilight realizes that Herald's plan is one big one of these — first, using Trixie to keep the Princesses and Bearers' eyes off his plans, and then using himself as a distraction to stop them from noticing the Outer Gods' arrival until it's too late.
The Man Behind the Man: Herald to Trixie. The Mane Cast and the Princesses have encountered her, and while they know Trixie is working with a mystery stallion, they assume she's the dominant party, and aren't aware of Herald's higher plans.
He reveals himself during the attack on Canterlot, and the heroes are all shocked to realize that they've been chasing the wrong pony.
My God, What Have I Done?: Rainbow Dash's reaction when she goes after Herald and collapses the windmill he's in, only to find the Cutie Mark Crusaders in the rubble.
More of a "What Did I Almost Do", but Applejack when she almost kills Trixie in blind fury.
Nice Job Breaking It, Hero: When the Princesses consider canceling the eclipse in light of everything that's happened, Spike convinces them not to, because that's not what Twilight (who is currently catatonic) would want. As it turns out, the eclipse is key to Herald's plan.
A flashback shows that Nyarlathotep was able to shrug off the thermonuclear explosion Celestia used on him last time he showed up.
Subverted with the Elements of Harmony, which not only does he admit might actually work on him, when unleashed vaporize him completely. While it doesn't kill him, it still banishes him back from whence he came and allows Celestia and Luna time to seal the way he got to Equestria before.
Not Afraid of You Anymore: Twilight and company ultimately feel this way about Herald/Nyarlathotep, who they're facing in his true form, as by this point, he's pretty much done everything he could to them, so they have nothing more to fear from him that they haven't already faced. This is unfortunate for Herald, who was banking on them being too afraid of him killing them to blast him point blank with the Elements.
What was there to be afraid of, that it hadn’t already shown her?
Oh Crap: Everyone in Ponyville when they see the Dark Young for the first time.
The Princesses when they begin to realize what they're dealing with.
Twilight, doing research into what's happening, finds references to the "Messenger of the Old Ones" and its multiple titles, including "Herald of the Outer Gods"... and realizes that the stranger she's alone with just introduced himself as "Herald".
The rest of the Mane Cast and Luna when they realize that Rainbow Dash rushing after Herald after he drove Twilight insane is a trap he's laid.
Celestia and Luna when they finally confront Herald and recognize him as Nyarlathotep.
They have another one when they realize that the eclipse is weakening them, and that they, not the Element Bearers, are Herald's targets.
Everyone else's reaction when they see the results of the above.
One-Winged Angel: Nyarlathotep takes on his true form when fighting the Princesses outside reality.
The Princesses essentially do so themselves during the same fight, becoming beings of pure power that no pony would recognize as them.
Only I Can Kill Him: Subverted. While the Elements do finish Herald off, it's only because Spike sent him to fight the Princesses, who not only weakened him but drove him into a Villainous Breakdown that gives them the opening to do so.
Out-Gambitted: Nyarlathotep is able to defeat Celestia and Luna first by hiding his identity, and then by making it look like the Element Bearers were the primary target — when, in fact, it was the Princesses themselves.
Perception Filter: Herald uses one to allow himself, Trixie, and the Dark Young to sneak into Canterlot.
"What did you do to the Princesses, you bucking son-of-a-bitch?!"
"The Reason You Suck" Speech: Nyarlathotep gives one about ponies in general, stating how easily they snap when they experience their insignificance in the universe, and the Element Bearers in specific, describing how easy they were to manipulate.
Roaring Rampage of Revenge: When Applejack runs into Trixie again at Canterlot, she goes into a blind fury over everything they perceive her as having done (primarily what happened to Apple Bloom and her friends) and nearly beats her to death before Rainbow Dash stops her.
Sadistic Choice: Nyarlathotep pulls one on the Princesses when they confront him — They can banish him and thus stop his plans, but he's stolen the Cutie Mark Crusaders' souls, and will take them with him if he goes.
He pulls another one shortly after, where he tells Shining Armor to either stay and protect the Bearers (who he probably won't hurt yet) or go and save his troops who are being attacked by the Dark Young (who will kill all of them). Shining reluctantly picks the latter.
"I enjoy a good hero — they're so predictable. One little nudge and off they run towards the screaming."
Sealed Good in a Can: With the Princesses weakened by the eclipse, Nyarlathotep is able to banish them outside reality. He admits it's only temporary, but also that by the time they get out it'll be too late.
Sequel Hook: After everything's over and done, Celestia brings up the possibility that Herald may have had backup plans. We then see that this is true, as he somehow managed to impregnate Fluttershy.
Soul Jar: Literally — Nyarlathotep rips the Cutie Mark Crusaders' souls out and sticks them in a jar, keeping them as leverage. Twilight restores them at the end of the story.
Tele-Frag: How Twilight, Shining, and his guards kill the Dark Young — they teleport inside them, causing them to explode.
Herald drives Twilight insane by filling her mind with all his knowledge of himself and the Outer Gods. Even after she pulls herself back, the knowledge stays at the corners of her mind, threatening to drive her insane again.
This backfires on him in the end, as him having done this to her is part of the reason she decides she's Not Afraid of You Anymore; he's got nothing left to frighten her with he hasn't already shown her.
Twilight offhandedly references expies of a couple of other Mythos tomes when researching what's going on.
Total Eclipse of the Plot: All this just so happens to be occurring in the days leading up to the first solar eclipse since Luna's return. And naturally, it's a key component of Nyarlathotep's plan, for two reasons: 1) at the height of the eclipse, the Princesses' powers are diminished, and 2) it appears to be part of the alignment necessary to release the Outer Gods.
Unwitting Pawn: So far, pretty much the entire cast has been this to Herald.
Villainous Breakdown: Herald actually gets angry when the Princesses, in their true forms, begin to win against him, damaging him faster than he can heal, symbolized by his mask being cracked when he returns to the mortal plane. While he maintains his composure, he loses enough of his Genre Savvy to leave himself wide open to the Elements of Harmony.
Herald: “Your Majesties... you are beginning to frustrate me...”
Villain Song: Subverted. When Nyarlathotep's plans seem to have succeeded, he comments that he has the sudden urge to break into song... but decides not to indulge.
Wham Line: When Nyarlathotep is alone with the Princesses, who are stopping him from going after the Element Bearers.
Nyarlathotep: Why did you assume I was after them?
When The Planets Align: As the title suggests, the plot is following the Mythos cosmology of the Outer Gods returning when the stars are properly aligned.
Worf Had The Flu: Herald easily defeated the Princesses, but only because they were weakened by the eclipse. Later, when fighting him together outside of reality and at full strength, they actually begin to overpower him, damaging him faster than he can heal.
Would Hurt a Child: Herald did something to the Cutie Mark Crusaders that left all three comatose, and then tricked Rainbow Dash into thinking she's the one who hurt them.
Specifically, he ripped out their souls, in order to use them as leverage against the Princesses and Element Bearers.
And then, he throws the jar containing their souls off the Canterlot waterfall, just to make the Bearers suffer.
The knowledge Twilight gets about Nyarlathotep when she sees his face includes the fact that he likes to have societies sacrifice their children to appease him, for the fun of it.
You Are Not Alone: When faced with the final fight against Nyarlathotep's full might, Twilight nearly loses hope and relapses back into insanity, before her friends remind her that they're there beside her. This gives her the strength to keep fighting and they proceed to curbstomp him with the Elements.