My Little Denarians (also available at FF.Net) is a The Dresden Files/My Little Pony: Friendship Is Magic crossover fanfic by Chengar Qordath. After the events of Forever!, a previous short story in which Harry accidentally summoned Pinkie Pie to his kitchen, her brief presence on Earth turns out to have major repercussions: Nicodemus learns of Pinkie Pie and by extension, of the possibility of travelling to various fictional universes through the Outside. His team of Denarians arrives in Equestria just at the start of the second season, making the episode go off the rails in hope of bringing Discord to Earth. Now, to save both worlds, Harry must save the mane six - not just from the effects of Discord's brainwashing but from the corrupting influence of the black coins...Now complete.Compare and contrast The Dresden Fillies.Although all effort has been taken to mark spoilers appropriately, the fanfic is set after the Dresden book Ghost Story and Late Arrival Spoilers may slip by. Be warned.There is now a sequel. Titled Dresden Gets Schooled (FF.Net link), it is set after Cold Days and will place Harry in the events of Equestria Girls.
My Little Denarians provides examples of the following tropes (Dresden Gets Schooled has its own section below):
Accordion Man: Discord's powers include cartoon invulnerability. Harry also contemplates how cartoon invulnerability could be used, like for example, surviving the backlash of a certain powerful ritual spell.
Action Girl: Nearly all of the Mane Six at one point or another, but Rainbow Dash and Applejack especially. And Lash.
Added Alliterative Appeal: Harry notes with dismay that his stay in cartoon-land may have changed his thinking process somewhat.
Harry: Wait... Why am I thinking in alliteration? Being in cartoon-land is really starting to mess with my brain.
Also used by Pinkie (of course): "Chilly Cherry Chocolate Chive Chili!"
Also sort-of how Lash defeats Lasciel. She explains that there is only room for one soul in the coin, and that by replacing Lasciel, and thus killing her, Lash has gained her powers and angelic status. She turns it down, however, as seen above.
Badass Boast: At one point Harry intimidates a demon by listing all the Denarians he has killed since the beginning of the story. He notes that not all of what he said was necessarily true, but adds to the intimidation factor anyway.
Bad Liar: Applejack's inability to lie gets referenced a few times.
Discord pushing Celestia's Berserk Button so that she exhausts her powers trying to hurt him and can be easily captured. Note that he did have enough raw power to do it the hard way - it was just more fun to use trickery.
Harry's plan for defeating Nicodemus - hope a Scheherezade Gambit manages to hold Nicky off killing him long enough for Sanya to run him through. Which also depends on Sanya still having enough fight left to do so.
Be Careful What You Wish For: As soon as he learns about the possibility of travel between worlds, Harry wishes for a chance to visit Star Wars. By the end of the story he gets his wish and as it turns out, almost getting beheaded by Darth Vader is the high point of this trip.
Berserk Button: Discord casually stomps on Celestia's long enough to distract and kidnap her.
Nicky having Derpy shot makes Harry boil with rage. Immediately following that, Jenkin's death at the fangs of a Denarian-possessed rabbit, and Nicodemus' casual mockery of it makes Harry abandon all pretense of snarking and scream right into the phone that Nick is "fucking dead."
Beyond the Impossible: Everyone thought that it was impossible to destroy a Denarian's coin, leaving Harry shocked when Lash's victory over Lasciel results in just that happening.
BFG: The mega party cannon. As well as the party artillery. And party bombs. Taken Up to Eleven with a party heat-seeking missile launcher.
Also, several Denarian cultists bring 50-cal machineguns with them.
Blown Across the Room: A mutual case between possessed Fluttershy and Harry. Only instead of a room, it was across an entire mountain.
Bob from Accounting: One of Harry's Imagine Spots contains "Bob the cultist", an unfortunate servant of Nicodemus forced to watch and rewatch the first season of ponies to gather intelligence on their targets.
Break the Cutie: All of the Denarian's holders, to some extent, after they have realized what they did under the coin's influence.
An especially harsh example for Twilight. She was completely and utterly broken, in mind, body, and spirit.
Bring News Back: Before going for a really desperate plan, Harry persuades Lash to leave the group and warn everybody in case he fails.
Broken Bird: Twilight has a severe case of PTSD after returning from the moon. She's even more timid than Fluttershy.
Brought Down to Normal: Celestia, after being hit by Harry's Friendship Nuke. Fortunately, it will only take about a week for her full power to return, unlike Luna who had to take a full year to recover after being healed by the Elements of Harmony. Unfortunately, a week is more than enough time for Discord and the Denarians to turn Earth into a crater.
Brown Note: Harry has a bit of a Brown Note when he sees Discord swimming in the Outside instead of hanging around Equestria.
Also occurs when Harry sees something really, really terrifying. Like an angry Discorded Celestia.
Harry: If I pissed myself in terror because of a girly pony princess, I would never live it down.
Buffy Speak: In chapter 26, 'Even without pain as a factor I was limping more than ... something that really limps a lot.'
In chapter 20:
Harry:a poker face to rival … I dunno, something with a really good poker face.
Bunny-Ears Lawyer: Derpy. She is every bit as ditzy as she looks, but that means she can get away with any level of Obfuscating Stupidity - and being a postmare allows her to go almost anywhere without looking suspicious.
She is Luna's personal spy for the resistance, who believes a variety of equipment means different flavors of muffins.
Bystander Syndrome: When Harry and the girls get back to Earth, this is pretty much the main reason no one else except Lash, Rashid the Gatekeeper and Sanya do anything to help. To clarify, it would be perfectly possible for one of the All Powerful Bystanders to help, but the cost to do so is so high, it is better to wait for some other sucker to pay the butcher's bill.
The Caligula: Discorded Celestia and Possessed Cadance. They try to paint Luna as this but no one wants to believe it.
Call Back: In chapter 26 Harry pulls the same "punt car at villain" move he used back in Dead Beat.
The Cameo: While moving between worlds, the characters briefly encounter Deadpool, Cupcakes Pinkie and Littlepip. Pinkie Pie herself seems to have making random cameos as a hobby. Cupcakes stops being a cameo in Chapter 21.
Combined Energy Attack: How Harry ultimately defeats Discorded Celestia, by tapping into the friendship power of the large crowd of ponies who he and his co-conspirators had successfully goaded into taking a stand against Celestia's new oppressive regime. Though Harry notes that it isn't as powerful or as focused as the Elements of Harmony, it operates under the same principles and does the job.
Confusion Fu: Derpy helps the heroes greatly through acts of seemingly random clumsiness.
Harry, after Derpy smashes through a pillar to obstruct their pursuers: How does a single pony manage to keep smashing through solid stone?
Continuity Nod: Harry references the dropping of the old Soviet satellite that happened in Death Masks. Also from there, '(being able to forget the time I soul-gazed a Denarian would be nice)'
“Saying you’ll snipe someone I care about unless I chat with you? You’re slipping Nicky. Last time you tried that trick, you were gonna shoot Molly if I didn’t make nice with you. I expected a little more variety.”
Cool, but Inefficient: Harry accuses the outfit Rarity gave him of being this in chapter 26. "The outfit Rarity had me set up with might be wonderfully stylish, but it was woefully lacking in the keeping-me-alive department."
The Corrupter: Discord and the Denarians, natch. Discord also claims that he helped turn Luna into Nightmare Moon.
In chapter 23, Harry is deeply concerned that he has become this in regards to Twilight.
Corrupt the Cutie: Harry unintentionally performs a mild version of this by expanding Rainbow's vocabulary to include human swear words. He also wonders if Applejack being a smartass Deadpan Snarker in chapter 19 is his fault. In chapter 23 he wonders if he's turning Twilight into a monster.
Cosmic Plaything: Harry is convinced the universe hates him. Events in canon and in this fic support that idea.
Damn You, Muscle Memory: Lash and Tessa, having actual swordfighting experience unlike Harry, can't let go of their training when they take up lightsabers. Later given as the reason for why Harry didn't just escape to the Outside; having spent the whole of his life being told that knowledge and use of the Outside is a capital offence, in the high stress situation it fails to enter his instinctual responses.
Dangerous Forbidden Technique: Words of Creation, with a capital W. Unusually for the trope, it backfires completely, not only doing no damage to the bad guys but also taking Lash out of the battle and stunning Harry, which Discord then uses as a basis for his Breaking Speech.
Dangerously Genre Savvy: Discorded Celestia, keeping the elements at hand rather than in some secluded location. Also They aren't really in her throne room - it's a trap.
Darkest Hour: The end of Chapter 5. The ponies are captured, Discord is free, Nicodemus is planning to use the ponies as hosts, Harry is discorded, Lash is gone, Celestia is gone, Luna is missing, etc.
The ending of chapter 13, with the Elements being a trap and possessed Cadance. And then chapter 15, with Luna sent back to the moon and Rainbow Dash apparently dead.
Dark Fic: A half-example, since it's dark for a My Little Pony fic, but about on par with canon for The Dresden Files.
Harry's idea to disrupt a magical storm by siphoning energy from it. Fortunately, the realization of what exactly he is doing dawned on him just in time to avoid getting fried. He immediately fell to the trope again, deciding to fight possessed Dash in the open.
Rashid accuses him of this when givings souls to the ponies, who are Outsiders.
Harry has this thought in chapter 26 when he tries to burn away Nicky's Living Shadow... that was trying to crawl up his pants.
Dissimile: Harry's attempt to describe Lasciel. "‘A rebel angel amongst rebels.’ Sort of like James Dean, except with fire and brimstone instead of motorcycles and leather jackets."
Dissonant Serenity: Nicodemus does this a lot, though Harry finds it more annoying than creepy.
He also gets frustrated when his best snarking attempts just bounce right off him.
Divide and Conquer: In chapter 25, Discord attempts this on Harry and the ponies when he realizes his attempts to rewrite the ponies' personalities via the writers isn't working. He offers to teleport Harry to Nicodemus giving him a chance to end the Denarians' evil for good. Harry knows Discord is trying to separate them, but the opportunity to stop Nicodemus is too tempting. He decides to trust the ponies to triumph without him and, with the encouragement of the ponies, accepts Discord's offer.
Elite Mooks: Nick's cultists. They wear body armor, use sniper teams and flanking tactics, arrange ambushes, coordinate assaults, and armor their cars. Harry thinks they seem almost too competent to willingly work for someone like Nicodemus.
Eldritch Abomination: Discord in the Outside. The sight of an embodiment of Disharmony and Chaos free of cartoon conventions greatly disturbs Dresden, who is no stranger to seeing horrifying things.
Emergency Transformation: Defied. Harry chooses not to give a dying Jenkins a coin because of how easily the coin and the decision would corrupt them both.
Endless Daytime: After Celestia is corrupted by Discord, she brings this about.
Et Tu, Brute?: Discorded Shining Armor refusing to help Twilight against Discorded Celestia, even sealing her in.
Eureka Moment: Harry has several, pushing the action forward whenever the group gets stuck.
Harry: Y'wanna know the simple truth, Nicky? If you ever were some kinda wanna-be hero, then you jumped off the slippery slope so long ago that your feet don't even remember what it feels like to touch the ground. If you're a liar, then you're a crappy one. Either way, I'm not buying the shit you're selling, because the simple truth is that you're an asshole.
Exactly What I Aimed At: Lash throws her lightsaber at a Denarian and it seems to have only scratched her ... but she was not aiming for vital areas: she was aiming for the coin.
Exact Words: Invoked. Harry may have promised to let Cadance go, but when he starts getting doubts about his ploy, Rarity comes to his aid by saying that she never made such a promise.
“Of course, sometimes I’m shooting at things that find bullets of any size annoying instead of painful.” Later in the very same chapter, the character who said that falls victim to Once Is Not Enough.
Full Name Ultimatum: Harry gets one from Lash for teaching Rainbow Dash to swear. He thinks that all women are capable of the feat, then wonders how Lash knows, since she has no experience as a human female mortal.
Game-Breaking Injury: Dash suffers a cracked rib while trying to subdue Fluttershy. She overcomes the pain through sheer stubbornness, but later on, the loss of agility proves a dangerous weakness when she gets between unconscious Pinkie and Magog, almost getting her killed.
Also, it is significant that by that time the radar is completely off. No cartoon Narrative Causality to protect the heroes anyomre
Gilded Cage: In chapter 20 after Harry lets himself and the Mane Cast be captured as part of his plan, Harry and friends are confined to a posh suite with nice furniture and fresh food, which is apparently the closest thing Canterlot palace has to a dungeon. Harry complains since he wants the authentic evil dungeon experience.
Glad He's on Our Side: After seeing what Twilight can do when angry, Harry is very glad she didn't take the coin.
Also with Celestia and Shining Armor. Harry notes later than Celestia, when going all-out, is pants-horseappling terrifying, and that Shining Armor is one of the few spellcasters who can give him a challenge.
Gladiator Games: Discord transforms Twilight's library into a huge arena for Denarians vs ponies showdown.
Go Mad from the Revelation: Traveling through The Outside will do this to anyone who doesn't have some sort of guide to lead them through. Harry wonders if Pinkie's frequent travels through The Outside have contributed to her barely-controlled cheerful craziness.
Also comes up during the first battle. Harry is facing an illusionist demon but can't use his Sight, for fear of seeing the true form of something really, really bad.
Harry makes sure Rainbow Dash won't see the pony-themed toy section in a shopping mall, fearing that it could result in a serious existential crisis.
Godzilla Threshold: Harry taking a hostage. Also, at some point the group discusses the possibility of contacting hell to Summon Bigger Fish. And Rarity using firearms. Things get desperate pretty quickly here.
Good Cop/Bad Cop: Denarian Cadance and Discorded Celestia. The latter is the bad cop.
Half Truth: Used by Discord to break Harry, tallying all the people that died as the result of his actions, while forgetting all he saved people with the same actions. Though considering the mind-boggling number, he may have just been outright lying.
He Who Fights Monsters: Harry fears that he's bringing Twilight down this path, thinking of Morgan as he does so.
Just when it looks like Harry and co. are about to successfully escape, Discorded Shining Armor catches up to him and traps the entire group.
Hostage Situation: Harry does this to Cadance. Shining Armor later does this to Diamond Tiara.
Taken Up to Eleven, when Denarian Derpy holds herself hostage.
I Am Spartacus: Sort of. The ponies declaring against Discorded Celestia which Element they would take up if a Bearer fell.
I Didn't Mean to Kill Him: Twilight assumed that our moon has an atmosphere, as Equestria's does, when she casts a banishment spell. It takes summoning a corpse back to convince her otherwise and triggers a Heroic BSOD.
I Did What I Had to Do: Harry, as usual. He notes that a man like him who did horrible things for the greater good has no business in a land of cheerful and innocent cartoon ponies.
Immortality Hurts - being able to regenerate from any injury as long as you have your coin is a cool power, but if your opponent is in an Unstoppable Rage and armed with a lightsaber, he will just keep chopping you up until he finds it.
Well, its debatable. The Denarians don't actually seem to experience pain, unless it comes from one of the Swords.
Imperial Stormtrooper Marksmanship Academy: presented by actual imperial stormtroopers. Harry complements them on their amazing marksmanship with no irony, since it would take an amazing amount of skill to point the gun at him and avoid hitting accidentally.
It's All My Fault: Harry is suffering from a bad case of this in chapter 16. Rainbow Dash's apparent death, Twilight's banishment, being suckered by Celestia's trap...he blames himself for all of it. And he's partly right.
It's Personal: If it wasn't before for Harry, it clearly becomes so once the villains make Fluttershy kill a defenceless man.
Again, after Harry finds out what happened to Twilight.
The fight against Lasciel is personal for Lash by default.
Mood Whiplash: Compare the beginning of chapter 13 to the end of chapter 13.
Or the beginning and ending of Skyrim battle
Mooks: Zigzagged. Though obviously weaker than Harry and the Mane Six in a fair fight, Canterlot royal guards, Denarian cultists and Imperial stormtroopers do manage to seriously inconvenience the heroes and become a credible threat when allowed to play to their strengths.
New Powers as the Plot Demands: Not only does Lash get a body as the result of visiting Equestria, when Harry is reduced to a broken heap by Dash' Meteor Move it turns out she can heal him, something extremely rare in Dresdenverse.
Scootaloo's desire to see Rainbow Dash again sees her calling out to a group of guard Pegasi, drawing their attention to the escapees. All the way up to the end, whether she gets chewed out for it remains unknown.
"In hindsight, taking Cadence hostage had been a bad move on my part. Apparently, it had inspired all the bad guys to follow my example and start pulling the hostage card too."
In chapter 24, Harry deciding to call Nicodemus's "bluff" and promptly cancel the fragile truce agreement once Rainbow Dash is safely back. Turns out the sniper Nicodemus had so casually mentioned had another pegasus in his sights from the start...
No Ontological Inertia: Discussed. "I guess demonic immortality doesn’t come with much in the way of ontological inertia."
Nobody Can Die: An important plot point, as the effect depends on the current setting. In Equestria, this is mostly true, especially for the heroes. Other worlds are much less forgiving. Discord and the Denarians have messed with reality enough that this is no longer the case even in Equestria.
Not So Different: Harry chides the ponies for eavesdropping on him and Twilight after they scolded him for reading her diary.
The Not So Harmless Punishment: In chapter 23, Twilight sends a bunch of cultists to the moon. She only wanted to send them there a couple days to give them time to think about what they did except in our reality the moon has no atmosphere. She is horrified when she brings back one of the cultists who turns out to be very, very dead.
Oh, Crap: Ptzriel when he realizes he is left alone against the mane six. Harry and his friends when Possessed Pinkie pulls out her array of weapons. Magog, when Pinkie pulls out a bazooka.
Chapter 13:Hey, corrupted Cadance. Fancy meeting you here.
Chapter 20: Um, Pinkie? Please put down the knife.
Chapter 21: The Denarians have taken the production crew hostage.
Chapter 22: Harry realizing that Mab manipulated him into violating the Seventh Law of Magic to tighten his leash. The Gatekeeper is also unpleasantly surprised when Harry reveals that he gave a bunch of Outsiders souls.
Chapter 23 gets 2 Oh, Crap reactions out of Harry in the span of about 3 seconds: First when Fluttershy gets shot and a moment later when it results in Twilight Sparkle going avatar state on the cultists
Harry in 24, first after realising how Nick has played him and then when the actual meaning of Nick's Exact Words dawns on him.
Oh My Gods!: Ponies use Celestia or Luna to swear or curse by.
Out-Gambitted: “I figured you’d look behind you when I disappeared, so I decided to pop up right in front of you."
Out of the Inferno / The Worf Barrage: Celestia tries to fight Discord, unleashing The Power of the Sun on him and actually melting a large part of the great hall in the process. Yet when the smoke clears, Discord is not only unharmed but casually backstroking in the resultant pool of lava.
Our Souls Are Different: Harry and Lash have them of course but it's iffy if anyone from Equestria has one.Until chapter 21, when, to keep Discord from affecting their free will, Harry gives each of the six Bearers of the Elements of Harmony a piece of his soul to mature into their own.
Pintsized Powerhouse: The Killer Rabbit. Realistically subverted in that with all its strength it still has a mass of several pounds, with all the consequences. Also there is only so much damage resistance one can give to a body this size.
The Plan: Harry has one to re-take the Elements of Harmony and defeat Celestia.
Playing Possum: Nicodemus, which causes his henchmen to get trashed without his support but lets him execute his Xanatos Gambit.Also, Lash, with a little help from her illusion magic.
The Power of Friendship: mostly played straight but with one interesting subversion - unlike the cartoon version, Rainbow Dash is "discorded" by getting her judgement skewed rather than by personality reversal - she is still fiercely loyal to her friends but blind to what has happened to them. The combination of denarius powers and genuine Heroic Resolve makes her extremely dangerous.
Ship Tease: A bit towards Pinkie Pie/Rainbow Dash at the end of the ninth chapter.
Even more in chapter 13 and it adds Lyra and Bon Bon to the mix.
Shoot the Dog: Harry's pragmatic side tells him to let Diamond Tiara die, reasoning that the life of one is an acceptable price for billions and that no one would miss the local schoolyard bully. He tells it to zip it.
Superpowered Evil Side: Subverted for Harry's possession. Subconscious resistance causes him to become a ridiculous Card-Carrying Villain, still dangerous but much less so than raw power might suggest. Played completely straight later when Harry briefly succumbs to the Dark Side.
Suspiciously Specific Denial: In the epilogue, 'I definitely didn’t sound as choked up as the climax of a chick-flick.' 'Yup, definitely not getting choked up at all.'
Sympathy for the Devil: Discussed in chapter 26 when Harry thinks that 'Seeing Nicky in the role of the grieving father struggling to avenge the death of his daughter might’ve made it just a bit harder to see him as a complete murdering psycho.'
Take That: In Star Wars, Harry is glad to see the Jedi Temple in ruins, as it means the prequel trilogy is already past.
'sending waves of agony shooting through her head as the alicorn cracked (the stuff unicorn horns are made of, not the misused term for a pegacorn)'
In 24, the three humans denounce the less-reliability of a Fabrique Nationale F2000.
Tastes Like Purple: The Outside. The fact that it also includes directions makes navigation an unforgettable experience.
Taught by Experience: After getting his arse kicked by possessed pegasi a few times, Harry forces Deirdre-possessed Derpy to the ground as soon as she tries to take flight.
Tempting Fate: The moment Harry thinks he can get out of a confrontation with the guards while having to protect the escapees, Shining Armor's barrier appears.
Lash's relief that Harry didn't start using annoying cold and ice-based puns after becoming the Winter Knight is shortlived since she admitted that in earshot of Harry. Harry immediately commences the punishment.
In 23 Harry is glad that he hasn't started using pony puns like "everypony". A few paragraphs later...
25 does this twice in rapid succession. Harry asks Discord if his duster would be taken away. That happens. Sanya tells Harry to look on the bright side as he still has his dignity. Discord replaces the rest of his clothes with "stiletto heels, a bright pink feather boa, and white boxers with little red hearts on them."
That Man Is Dead: - Used by Rarity in a fight against Fluttershy. Fluttershy proceeds to prove her wrong.
Twilight Sparke has had a week of Break the Cutie. She isn't particularly stable now. So don't threaten her friends. Just don't.
Same for Raindow Dash. She may be no wizard but at the speeds she can move at, normal people are Made of Plasticine. Also, she isn't very good at holding back her emotions.
Villain Exit Stage Left: Parodied. Possessed Harry attempts a Smoke Out but has not prepared the escape route and is still struggling with a window when the smoke clears.
Villains Want Mercy: Lasciel begs Uriel to save her when she realizes Lash has the upper hand in their fight to the death. Uriel refuses.
Also invoked when Harry finds Tessa. Harry refuses. Vehemently.
Warhammer 40,000: Discussed by Harry, who is quite glad not to have to go there.
Pinkie drops in there for a brief cameo on her way to Equestria.
Weak, but Skilled: In the context of the cast, Rarity. See her crowning moment of awesome.
We Can Rebuild Him: After spending the whole chapter on a race against time to save Rainbow Dash, Harry suffers a moment of Fridge Logic when he realises the group had access to all sorts of fictional realities, with their respective brands of magic and/or technology.
Wham Episode: Chapters 5, 10, 11 and 12: Discord and Nicodemus succeed in corrupting Harry and the girls, Rainbow Dash nearly dies fighting Magog, Discord has left Equestria (which is worse than it sounds), Luna admits that the "Nobody Can Die" law may no longer be in effect and furthermore, Twilight Sparkle IS ON THE MOON.
Luna is off fighting Celestia so who's going to help fight CADANCE?!?
Chapter 20: Okay, so Celestia's free of Discord's brainwashing, but the Rainbow of Light has left her powers drained as it did with Luna, and Twilight's in bad shape due to Discord and the Denarians' vile manipulations — oh, and Pinkie appears to have been taken over by her psychotic and evil alter-ego from Cupcakes, much to Harry's grief.
While Harry understands their reasons, he can't help but bitterly call out Celestia and Luna on leaving Earth to Discord and the Denarians while waiting for Celestia's power to return.
The Gatekeeper calls out Harry on violating the Seventh Law of Magic and ensouling Outsiders. He also calls Harry out on not asking him — the guy in charge of watching the Outer Gates — for help instead of chasing after the demons. He makes it clear to Harry that Harry's position as Mab's Winter Knight is the only reason the Council isn't going to execute him.
On a lighter note, Sanya makes a big deal about Harry reading Twilight's diary.
Shining Armour is a Barrier Warrior and lacks offensive spells (or the personality to employ Lethal Harmless Powers). Still he puts his abilities to good use, dividing the battlefield to thwart the enemy team tactics and allow the guard to corner individual opponents. Chapter 17 emphasizes this.
Contrary to what the popular saying claimed, when all you have is a hammer, it usually means you start getting extremely skilled at using a hammer and find all sorts of creative ways to use it.
And in Chapter 19, he manages to restrain Celestia, admittedly with Cadance's help, long enough for Harry and the rest to prepare their next move.
Having no healing magic of his own, Harry tends to use ice magic as an emergency means of stopping bleedings.
Willing Channeler: Rainbow Dash is brainwashed into this. The result is an insane boost of power, enough for her to whip up a full-sized tornado all by herself.
The Woman Wearing the Queenly Mask: Luna, which she drops temperarily while talking to Harry about the upcoming battle with Celestia, locating Twilight and Discord's possible successes.
Worf Had the Flu - used in-universe by Rainbow Dash. After getting saved, she can't stomach the defeat despite the circumstances and blames it on the demon, despite all the evidence to the contrary.
Worst Aid: In chapter 26 Harry pulls a hunk of metal out of his leg and recognises it might be doing more damage than leaving it in. Fortunately he can freeze over the wound to hold the blood loss back. Justified in that the iron was cutting him off from his Winter Knight powers.
Would Hurt a Child - Shining Armor holds Diamond Tiara hostage with a dagger at her throat in a bid to make Harry surrender. Harry takes this as proof that Shining Armor has also been Discorded, reasoning that anyone who was made the Captain of the Equestrian Royal Guard back when everything was still okay in the first place would normally be too good a person to threaten a child like that.
Xanatos Gambit - Nicodemus' plan to have the denarians fight the mane six - if they win, they will have eliminated the greatest threat to his Evil Plan. If they lose the ponies will be tired and vulnerable to attack - and since they have won, they will make much better hosts for the demons.
During their phone conversation in chapter 24, Harry suddenly finds himself very much wondering if his past canon "victories" against Nicodemus haven't instead served to make his enemy's position stronger all along. After all, a Denarian (especially a nigh-invulnerable one like Nicky) can fairly comfortably afford to take the long-term view and spin a half-dozen slowly unfolding flexible master plans while Harry is much more often compelled to make snap decisions whose consequences may come back to bite him later just to survive from one day to the next in his line of work...
You Have Outlived Your Usefulness: Discussed. "Or maybe instead of a limit on the magic, it was a case of the legions of darkness opting for the Darth Vader method of dealing with minions who failed them."
Dresden Gets Schooled provides examples of the following tropes:
Groin Attack: Human Rainbow Dash subjects Harry to one for kissing her. Repeatedly.
It's Personal: Michael agrees to go with Harry after Sunset Shimmer because her situation reminds him of Molly's case.
Off the Rails: One hell of a First Episode Spoiler follows. Harry and Michael, with the help of Human Rainbow Dash, break into Principal Celestia's office and grab the Element of Magic. Harry then uses a warning shot to scare Sunset Shimmer off smashing the portal and brings Sunset back to Equestria. Celestia then asks him to take her as an apprentice.