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Fanfic / The Arithmancer

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The Arithmancer by White Squirrel is a Harry Potter Alternate Universe Fanfic in which Hermione Granger is a mathematics prodigy. It is complete and covers Years 1-4, with a completed sequel, Lady Archimedes, covering Years 5-7. A third story, Annals of Arithmancy, which is set after graduation, was finished in March 2019.

Unmarked spoilers below.


  • Accidental Kiss: Harry and Ginny's lips touch by accident when he's rescuing her from the Lake and sharing a Bubble-Head Charm with her. She has the presence of mind to linger for a moment.
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  • Adaptational Badass: In addition to Hermione being such a math whiz, there is also Ron's chess skills, and the whole trio's, plus Professor Vector's, actions in the Chamber of Secrets.
  • Adaptational Villainy: In the sequel the author manages to pull this off with Umbridge — who was already a villain in the original novels.
  • Adult Fear:
    • The Grangers are creeped out that the Wizarding World can track one's movements unless concealed with magic.
    • In the epilogue Barty Crouch, who got away, keeps making attempts to kidnap his Happily Adopted child.
  • Alternate History: In this fic, the witch hunts began much earlier, as early as the 9th century.note  King Malcolm III didn't like that his predecessor was getting help from witches, and started an active persecution of witchcraft.
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  • Alien Geometries: Hogwarts runs on this. Not only do the interior's measurements not match the outside, the corridors have different measurements across different floors. And parallel corridors in a rectangle aren't necessarily the same length, even after testing that they all meet at right angles.
  • Anger Born of Worry: George to Hermione in the sequel's Chapter 57 when her insomnia-derived recklessness caused her to Apparate in front of the Weasleys' shop during a Death Eater attack and nearly get hit with a Killing Curse.
  • Armed with Canon: More literally than usual. Christian wizards and witches point out that the Bible only bans divination and necromancy.
  • As the Good Book Says...: As she studies soul magic in order to understand Horcruxes (including the one in Harry), Hermione purchases religious books. She later "borrows" a Bible while on the run from the Death Eaters.
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  • Ascended Extra: Professor Septima Vector.
  • Attack on the Heart: Hermione's medical research leads her to develop a variation on the Simple Strike Hex, which is no more powerful than being punched in the nose — but her version delivers that force directly to the heart in a way designed to cause cardiac arrest. And it can penetrate single-layer shields. She almost kills Bellatrix Lestrange with it, but another Death Eater was smart enough to revive her.
  • Attention Deficit... Ooh, Shiny!: Played for Drama. In the sequel, Hermione when she's on the run from the Death Eaters. She has so many projects and problems facing her that she has a hard time focusing on the most important ones.
  • Badass Boast: There are a number throughout the series, including a direct reference to Galadriel's "All Shall Love Me And Despair" speech. But perhaps the most impressive is when she snares a curse out of the air, deconstructs it while giving commentary, and collapses it harmlessly.
    • When Draco taunts her with the prospect of the Unforgivable Curses being legalised by Voldemort, she laughs at him.
      Hermione: Anyone who resorts to Unforgivable Curses doesn't have an ounce of creativity.
    • She's also fond of Archimedes' boast: Dos moi pa sto, kai tan gan kinaso.note 
    • When reassuring her parents that she can protect herself:
      Hermione: Look, you two are dentists. People joke about how you can strike fear into the hearts of the strongest men. But I've been studying your old pathophysiology textbooks, and I have magic.
  • Badass Bookworm: In this Alternate Universe, Arithmancers tend to be this.
  • Badass Longcoat: Hermione is gifted one made of Basilisk skin, as thanks from a group of Indian cursebreakers who were saved by her protective glasses. Aside from looking awesome, it also has potent spell resistance.
  • Black Dude Dies First: Lee Jordan dies in the battle of the Department of Mysteries, making him the first character to die "onscreen".
  • Blinded by the Light: Remus and Sirius suggest fighting a dragon with a Conjunctivitis Curse, but Hermione is concerned about whether Harry will be able to reliably hit its eyes. So instead, she invents a spell to extract a cloud of magnesium powder from the soil, which he can then banish at the dragon and have it ignited by the dragon's breath for a colossal flashbang effect. He ends up using three clouds at once, and completely incapacitates the dragon.
  • Blood Knight: Blaise Zabini, the only marked Death Eater to be considered innocent, joins the Reconciliation Committee established after the war. He's the most militant and bloodthirsty of all members, basically demanding the death penalty for all of the Death Eaters.
  • Body Horror: When Hermione begins devising curses she starts by digging into her parents' medical textbooks. The results are horrific. And when Hermione is done with Umbridge, she's almost unrecognizable as anything but abstract art.
    Hermione: Epidermolysis bullosa!note 
  • Bread and Circuses: Hermione literally shouts "PANEM ET CIRCENSES!" during the first Triwizard Task, although only a few muggle-born students understand her social commentary.
  • Broken Masquerade: A focus of the sequel, played for drama. Hermione realizes that keeping up the Statute of Secrecy will soon become mathematically impossible. She publishes her work, is immediately arrested for treason, and ultimately has to defend her conclusion in front of the International Confederation of Wizards.
  • Collection Sidequest: After the success of her magnesium extraction spell, Hermione tries her hand at collecting samples of each element (or in some cases, like sodium, simple compounds). The fact that she extracts them in powder form is an inconvenience, but she doesn't let it stop her, she just melts down the powder into an ingot, using homemade thermite for the tougher elements.
  • Corporal Punishment: It was never formally banned at Hogwarts, but Dumbledore used his power to forbid it. Umbridge, however, brings it back when she becomes headmistress.
  • "Could Have Avoided This!" Plot: After the drama and danger of the fake locket Horcrux, Hermione learns that Elf Apparition wasn't being blocked in the cave, meaning that Dobby could have transported them in and out.
  • Crazy-Prepared: After the war, Hermione has a big job on her hands emptying out everything from her extended handbag, from synthetic food to incomplete magic-infused runes to homemade guns to a collection of deadly poisons, nerve gas, and even chlorine trifluoride. And that's after she lost many of her possessions at Malfoy Manor.
    Hermione: C-4, C-4, more C-4. Why did I make so much C4?
  • Day of the Jackboot: Voldemort takes over the Ministry in Chapter 47 of the sequel, a few months earlier than canon due to Dumbledore's death.
  • De-Power: Septima Vector loses her ability to use arithmancy after she suffers traumatic brain injury due to being Crucioed.
  • Deconstruction Fic: Not the most extreme example, but the fic does point out certain inconsistencies in the characters' behavior, as well as the general weirdness of the wizarding world.
    • The first arc does a Decon-Recon Switch of the Chronic Hero Syndrome, pointing out that first years simply do not know enough magic to face a troll, which is defeated with a non-lethal One-Hit Kill spell cast by Professor Vector.
    • Kid Hero is deconstructed too, as everyone points out that a first year at Hogwarts would be curbstomped in a fight against an adult wizard and Harry's attempts to get to the Philosopher's Stone are seen as suicidal.
    • Later, the obstacles get a Difficulty Spike and Quirrelmort got through by cheating, using an obscure charm to make Vector's enchanted statues color-blind and causing a system failure that opens the doorway.
    • Hermione points out that Mandrakes are literally Person of Mass Destruction due to their lethal scream. If a malicious wizard put an amplifying charm on the plant it would result in the death of thousands. However Professor Sprout points out that the lethal effects are not instantaneous and that the scream cannot be reproduced artificially, such as recording the scream. And that a silencing charm will render the mandrake harmless.
  • Despair Event Horizon: The Basilisk attacks on muggleborns have such an impact on Hermione that by Christmas she's ready to either give up magic altogether or be transferred to another school.
  • Disproportionate Retribution: Hermione considers Azkaban — full of soul-devouring demons that cause clinical depression by their mere presence — to be too harsh for Rita Skeeter's actions, and her parents agree. Rita is shocked by their attitude, but not complaining about getting a better deal.
  • Doorstopper: The first two books have over half a million words each.
  • Dramatic Irony:
    • Played for Laughs; Hermione's letter home after the troll incident includes the phrase "It's not like an evil psychopath sneaks in and tries to kill somebody every year or something." In canon, almost every book focused on exactly that.
    • When the Grangers hire Dobby, he stubbornly insists on living in the cupboard under the stairs, claiming it's better than what he's used to and convenient for keeping him out of sight of visitors.
    • Professor Vector comments that an elf who wants wages is so rare that it's not something people normally consider, like an evil Gryffindor or a cuddly werewolf. This is in the summer before third year, where Professor Lupin teaches at the school and Peter Pettigrew is exposed.
    • The Hogwarts house elves are mistrustful of Dobby's desire to remain free, and assign him to the most menial tasks like cleaning the boys' toilets. Hermione starts to think about pushing for laws to protect him, and then realises that she wants anti-discrimination laws to protect the free workers from the slaves.
  • The Dreaded:
    • Voldemort to the Wizarding World. After an earlier death of Dumbledore, he curses his own name so that Death Eaters can track down his greatest enemies. Hermione uses a ritual to bind her tongue, which prevents her from speaking his name and triggering the Taboo Curse, which has a creative effect that the narrator refers to him as You-Know-Who.
    • Hermione, in the aftermath. Everyone knows that attacking her is a deadly mistake. And this is especially true among Dementors, whom she has made a personal project to eradicate. They call her The Destroyer.
  • Dream Reality Check: Daniel Granger pinches himself when McGonagall transforms his table into a tortoise to prove that magic exists.
  • Eaten Alive: Bellatrix Lestrange is basically nibbled to death by Hermione's Grey Goo backup weapon. It's a very unpleasant way to go.
  • Education Mama: Downplayed. The Grangers are distraught to find out that Hogwarts favors magic over science and muggle history, but when McGonagall informs them that it's possible to hire tutors and that magical education is only compulsory up to fifth year, they back down. For the most part they're the Open-Minded Parent.
  • Eldritch Abomination: The giant blob of dust and woodchips that appeared in the Battle of Hogwarts. Considering that it seemed to be the last thing to come down from the upper floors of the Grand Staircase, it was probably the top of the Grand Tower. But it was still animated by McGonagall's spell, and it still fought for Hogwarts.
  • Eldritch Location:
    • The upper floors of the Grand Staircase, as Hermione finds out.
    • The Third Task takes the form of a tesseract maze, which is mathematically regular, but hard to observe and far enough outside normal experience to mess with viewers' heads. Professor Septima thinks that Hermione could have made something worse.
      Hermione: Be glad I didn't, though. If you set the champions loose inside the Grand Antiprism, they could get lost for weeks.
  • Evil Counterpart: Voldemort's traitor Unspeakable, who is a spellcrafter almost as good as Hermione and can use a Pensieve to recreate her best work.
  • Exact Words: Hermione doesn't like lying, but freely makes use of this.
    • Dobby has been ordered to report to her parents when she's in a dangerous situation, as soon as she no longer needs his protection. When she doesn't want him to immediately report the World Cup attack to her parents, she is able to point out that by the time he's about to go, she's no longer in a dangerous situation, therefore the order doesn't have to apply.
    • As per canon, Dumbledore tries to stop her from giving Harry any sensitive information over the summer before fifth year. But what she actually promises to do is not to send any sensitive information that might be intercepted, and Dobby can deliver letters securely.
  • Existential Horror: Hermione does not cope well with learning about the Dementor's Kiss and realising that souls are real, but not necessarily immortal.
  • Faking the Dead: Hermione arranges for her parents to leave the country, then disguises herself as a Death Eater and stages an attack on their house, burning it to the ground and leaving behind two corpses with falsified identifying marks. She even convinces Snape to take the credit for it with Voldemort, so that there won't be an anomalous attack that no Death Eater admits to making.
  • Fate Worse than Death:
    • Beyond their already bad canon characteristics, ghosts also can't grow mentally and are trapped in whatever mental state they were in when they died and cannot get new memories. Nearly Headless Nick speculates that they might be able to pass on if they stopped being afraid of death, but since they can't mentally or emotionally develop, that can't happen.
    • Canon briefly states that the Dementor's Kiss is worse than death, but doesn't explore the subject. Hermione, however, is deeply traumatised by learning about what it does, and doesn't start to recover until she resolves to learn the Patronus Charm so she can defend herself.
  • Foregone Conclusion: Hermione's attempts to ensure that her map of the castle is architecturally correct fails because Hogwarts is always changing. She still tries to create a map without the correct measurements, though.
  • Foreshadowing: Early in The Arithmancer, after Hermione has her Freak Out about dementors, she worries about the hypothetical scenario of Luna being Kissed by one. Very late in Lady Archimedes, to Hermione's terror, that exact thing actually happens. And then she invents a ritual to undo it.
  • Fox-Chicken-Grain Puzzle: The Ravenclaw door gives puzzles in lieu of a password, of which this is one. Ginny suggests Cutting the Knot by casting Freezing Charms on the animals and conjuring a bigger boat, which the door deems an "acceptable alternative".
  • Friend to All Living Things: Hermione, though she takes exception at Dementors.
  • Get Out!: The Grangers have a downplayed version when McGonagall tries to recruit Hermione for Hogwarts, at least until she proves magic does exist.
  • Gilligan Cut: After Harry and Ron miss catching the train in second year, all their friends are discussing how Molly and Arthur probably used the Floo Network to get them to Hogsmeade and are enjoying butterbeer. Cut to Harry and Ron on the Knight Bus.
  • Godzilla Threshold: Hermione crosses this during the final battle. She ultimately kills Bellatrix with her invention, The Deplorable Word, which she spent most of the book trying to keep secret.
  • Good with Numbers: Hermione; that's the main premise.
  • Grey Goo: Hermione worries that this is possible with the use of transfiguration and runecraft. It is.
    Hermione: Qanenu.note 
  • Groin Attack: Ginny is present when Peter Pettigrew is unmasked, and promptly kicks him between the legs for having previously (in his rat form) watched her get dressed. A few minutes later, Hermione learns that he watched her too, and kicks him again.
  • Happily Adopted: The son of Bertha Jorkins and Barty Crouch Jr, who is adopted by Septima Vector after the Battle of Hogwarts.
  • Head Desk: After having had three crazy years of Hogwarts, this is Hermione's reaction to Harry's name coming out of the Goblet of Fire.
  • Heart Is an Awesome Power:
    • Harry is not very impressed by the spells Hermione invents for him before the Second Task — until she makes him try them out. He quickly discovers that her strobing green laser is very jarring if it gets you in the eye, and when cursed to speak in iambic pentameter, he can't successfully cast a wide variety of spells, including those that might lift the curse. Cedric is later saved by learning to cast the green laser, because it travels at light-speed and throws off Barty Crouch's aim at the last moment.
      Hermione: I think I'll leave it on and see how long it takes for people to notice.
      Harry: Hermio-n-n-NEE!
      Hermione: That's what you get for criticising my spells, Harry.
    • All her life, Hermione has had to deal with people asking, "What is maths good for?" The answer is that it lets her plumb previously unknown depths of magic, from molecular rearrangement that works like permanent Transfiguration without the usual five exceptions, to the invention of a plethora of new hexes and curses with remarkable effects like bypassing shields, to successfully using Ravenclaw's Diadem.
  • Homeschooled Kids: In her fifth year, Hermione leaves Hogwarts after Christmas and gets tutorship from Slughorn.
  • Horrifying the Horror: Even a pack of Dementors is scared of Hermione after she kills one of them.
    Hermione: Boo!
  • I Am Not Left-Handed: Hermione plays this 100% straight in her exhibition duel against Seamus Finnigan, and revels in the opportunity to quote it in full.
  • I Did What I Had to Do:
    • Hermione isn't happy with Dumbledore playing The Chessmaster with people's lives, and he doesn't enjoy it either, but he maintains that he is doing what he believes to be best.
    • Hermione herself is on the other end of this when her parents are upset by how she has become hardened to death and killing.
      Hermione: I'm not going to become a murderer, Dad. I'm not going to sink to his level. But I will defend myself and my friends. With deadly force, if necessary.
  • I Think You Broke Him: Stated by George when Hermione pays Dobby to help Winky get cleaned and sobered up, and insists on trying to help her pull herself together and get back on her feet. The other elves just stare, with their whole cultural background making the situation incomprehensible to them.
  • If You Ever Do Anything to Hurt Her...: Subverted when Dan has an "obligatory father-daughter's boyfriend talk" with George; he says This Is the Part Where... he's supposed to threaten a root canal without anaesthesia, but admits that Hermione is far scarier than he is, and if George hurts her, she will take revenge.
  • Immunity Disability: Hermione, Lavender and Parvati have a very difficult time getting Hagrid presentable for the Yule Ball, because his hair is resistant to magic.
  • Intrinsic Vow: Hermione's devotion to maths means that she is able to throw off the Imperius Curse when told to write 2+2=5.
  • In Spite of a Nail: Because of The Stations of the Canon being at play, this trope is played straight such as in these cases:
    • The barrier at King's Cross is still sealed and Ron still gets a Howler from his mother.
    • Dumbledore still dies but it's Draco not Snape who does it.
    • The Ministry still falls to the Death Eaters.
  • It Is Pronounced "Tro-PAY": Ginny's name is Ginevra, not Virginia which is why she's annoyed when Rita Skeeter misnames her in one of her articles.
  • Ley Line: Britain's ley line network plays a part in the second and third fics, being how the ministry of magic maintains national spells. Most Wizarding homes are built on ley lines and their defensive wards tap into the energy from them. At one point Hermione exploits continental drift in the ley lines to break into a Death Eater mansion.
  • Literal Metaphor: Cedric Diggory survives in this continuity, but as Hermione puts it, it cost "An Arm and a Leg, and no, that's not a figure of speech".
  • Loophole Abuse:
    • Quirrelmort gets through Professor Vector's trap by using a color-blind charm on her enchanted statues.
    • Underage wizards and witches can use wandless magic outside of school, as long they do not use it in front of Muggles that are not a Secret Keeper. Hermione makes use of this just to get on even footing with pureblood children, who exploit the more egregious loophole that the Ministry can't tell who cast a spell (only what and where) and therefore ignores all spellcasting in magical homes.
    • Runes can be used to replace wands in potion making, allowing muggles to brew potions.
    • After refusing to be a hostage for the Second Task, Hermione and Dobby are not allowed to have any contact with the Champions. But Harry already has a communication coin from her.
    • Umbridge bans teachers from giving students any information that isn't related to the subjects that they're paid to teach — so Hermione hands Professor Vector a coin and they continue discussing advanced Arithmancy as usual. When Umbridge finds out and bans teachers from teaching any classes outside the approved curriculum, Professor Vector starts paying Hermione a sickle per week to teach her "Advanced Topics in Mathematics".
  • Love Potion: Reconstructed; Hermione is quite displeased to learn that the Twins plan to sell them given the ethical problems, but they explain that they're deliberately developing mild versions that won't be more than pranks, just making someone compose poetry or blush or at the most give a single kiss and then snap out of it. Of course, they do some experimenting on themselves first...
  • Mama Bear:
    • Harry doesn't fully grasp how bad it is to have to steal an egg from a nesting dragon, until Hermione offers him a choice between fighting Bill Weasley or kidnapping Ginny from under Molly Weasley's nose. Upon considering that, his face goes pale and he concludes that he's going to die.
    • When someone attacks her and her children on Halloween, Hermione curses the area around him into a smoking ruin. She's surprised to find that he's still alive afterward — though he looks like a nightmare that she doesn't want the children to see.
  • Medieval Stasis: Played for Drama and Played with. The Wizarding World seems perpetually stuck in the 17th/18th centuries, with an extremely authoritarian government that literally controls the press and exerts influence over education and academia, as well as seeming to lack any concept of civil liberties. On the other hand, the Wizarding World seems to be ahead of the muggle world regarding religious tolerance and sexuality (remembering of course that Harry Potter is set in The '90s).
  • Mindlink Mates: After doing a Hollywood Exorcism ritual to remove the Horcrux inside Harry, one of the consequences of the light magic is that it turns Harry and Ginny into light-oriented horcruxes for each other. Deconstructed at first, it is very difficult to get used to and has a number of unpleasant side effects. In the beginning they can't even look each other in the eyes without intense pain, and being unable to be physically separated is not as fun as it sounds. Things work out well in the end though.
  • Misfit Mobilization Moment: After spending a year and half on the run from the Death Eater-controlled Ministry, the Battle of Hogwarts is this for Dumbledore's Army and the Order of the Phoenix.
  • Monumental Damage: Hogwarts Castle was so badly damaged by The Siege laid by Voldemort's forces, that in the aftermath McGonagall declared the castle uninhabitable and the survivors had to create a tent camp by the carriage stand.
  • Mundane Solution:
    • Basilisk kills with a stare? Use sunglasses with lenses of a certain color designed to filter out the yellow of its eyes. Although "Mundane" is selling what they do a little short — while the initial method of wearing sunglasses works, Hermione invents a spell on the fly to figure out the precise wavelength of light needed to block it out. And better? With them, she's able to look the Basilisk in the eye and only feel like she's got a migraine, rather than getting knocked out, paralyzed, or killed.
    • Instead of waiting a long time to get the Firebolt checked out by the teachers, they just send it back to the manufacturers and borrow a loaner until it can get checked.
    • Instead of flying a car to Hogwarts when Dobby seals the platform, Ron and Harry take the Knight Bus.
    • When trying to get at the Stone, Quirrell just steals the mirror the Stone is inside of, rather than sitting around and trying to puzzle it out in Hogwarts. He's still stopped, though, because the mirror was so big that it limited his escape paths.
  • My Skull Runneth Over: Xenophilius Lovegood only lasts two seconds wearing Ravenclaw's Diadem before passing out. Hermione copes better and can actually use it, but needs to block out all unnecessary sensory input to reduce the load.
  • Mythology Gag:
    • One of Ginny's nightmares after surviving being taken into the Chamber of Secrets is of Harry getting bitten by the basilisk after having to slay it alone because Hermione has been petrified and Ron has been blocked by a cave-in, just like what happened in canon. Except without Fawkes saving him. Hermione gets a feeling that this is exactly what Harry would've done had he actually been in this situation.
    • After Hermione and George attend the Yule Ball together but decide not to try a long distance relationship, her next visit involves hugging Harry and Ginny and several other friends, then awkwardly pausing with George and mutually deciding to shake hands. (Note that this happened in the movies with Hermione and Ron, not the books.)
    • When Hermione, at the breakfast table, promises payback if Rita Skeeter is using illegal means to get her stories, one of the other girls states, "You know, you're scary sometimes, Hermione? Brilliant, but scary."
  • Nails on a Blackboard: One of Hermione's efficiency-oriented jinxes for low-powered casters produces a cone of dissonant sounds similar to this.
  • A Nazi by Any Other Name: The Death Eaters and later the Ministry when they take over.
  • Noodle Incident: A clan feud between Fleur Delacour and another part-Veela apparently came to a head when when their class brewed Love Potions, but the details aren't stated, except that it ended with both of them in detention shovelling out the stables, and exposed several unexpected relationships amongst the seventh years. Hermione knows more but wishes she didn't.
  • Not His Sled: The climax of each year is always different than it is in the books.
  • "Not Making This Up" Disclaimer: Hermione decides to prove the existence of a sixth Principal Exception to Gamp's Law of Elemental Transfiguration, namely, radioactive material, not for the prestige such an accomplishment would bring, but because she's terrified that someone might try transfiguring antimatter, and proving the impossibility of radioactive transfiguration is the first step in proving the same of antimatter. When she explains this to her parents in a letter home, she has to clarify that it wasn't a joke.
  • O.C. Stand-in: Being told from Hermione's perspective, we get to see the teachers that she, rather than Harry, interacts with, particularly Vector.
  • Oh, Crap!:
    • Professor Vector gets a fairly large one when Hermione reveals that her experiments could potentially create antimatter. Or at least, she gets one once Hermione explains what antimatter is.
    • Hermione is woken up by Harry's message telling her that the first Triwizard Task is dragons, and later insists that her room mates must have dreamed the words she said in response.
    • At first, Harry doesn't think that stealing an egg from a nesting dragon sounds all that bad; at least he doesn't have to fight it. Then Hermione points out how Molly Weasley would react to someone kidnapping Ginny, and Harry decides he's doomed.
    • Being very familiar with goblins, Bill quickly grasps the implications of Hermione's matter rearrangement spells, which is scary enough, but she isn't planning to make waves. And then she tells him that within a few decades, Muggles will be able to make diamonds using similar techniques.
      Bill: Remind me to take an extended holiday in Siberia when that happens.
  • The One Thing I Don't Hate About You: Snape grudgingly admits that Hermione's potions publication was impressive and that he wouldn't be opposed to teaching her if she elected for independent study.
  • Our Ghosts Are Different:
    • Ghosts are Barred from the Afterlife and exist in an endless cycle, unable to grow mentally or gain new permanent memories outside of exceptional events.
    • There is an interesting contrast made with Portraits, which can learn and form new memories but have no capacity for creativity or true insight. Between a Portrait and a Ghost you would have a complete person.
  • Pædo Hunt: Downplayed. When the Granger read Hermione's Hogwarts letter they're creeped out that wizards can track the movements of children.
  • Personality Powers: Hermione considers inventing a Tooth-Drilling Hex for Harry to use in the Triwizard Tournament, but eventually decides to save it for herself.
  • Pet the Dog: Hermione helps Filch make a potion using rune clusters as part of her paper. He's so happy that the Twins thought it was the end of times.
  • Pop-Cultured Badass: Hermione loves making literary references and nerdy jokes, particularly in front of Wizards who have no idea what she's quoting.
  • Powder Keg Crowd: Umbridge's attempt to stop Septima from rescuing Harry and Hermione from the Ministry of Magic marks the final straw for Dumbledore's Army, resulting in a riot that ends with Umbridge getting blasted across the room.
  • Rage Breaking Point: It takes a lot to push Hermione over this line, but it can be done. Umbridge found that out the hard way.
  • Rant-Inducing Slight: After nearly being Kissed by a horde of Dementors, Hermione just can't take Minister Fudge's pleased comment that they caught Sirius Black, and blows up at him for his actions in setting demons around a school.
  • Rape Is a Special Kind of Evil: Bertha Jorkins was held hostage and brutally raped by Barty Couch Jr for four years, and eventually became pregnant. She's rescued by Snape when the DA takes over Hogwarts from the Death Eaters.
  • Reality Ensues: Hermione's parents grow increasingly distrustful of Hogwarts' commitment to student safety with each passing year. After she is nearly kissed by a Dementor, the Grangers force her to transfer to Beauxbatons.
  • Real Witches Love Jesus: It seems that Hermione is a Christian in that she believes in God and immortal souls. This is why she is so shocked to find out that the Dementors might be capable of destroying souls, and has a minor existential crisis about it. Her faith is ultimately vindicated to an extent when she figures out how to kill a Dementor and the souls it has trapped are released.
  • Reasonable Authority Figure: Arithmancy Professor Septima Vector is this to Hermione.
  • Red Herring: In Lady Archimedes, Hermione spends much of Chapter 77 searching for living wizards or magical creatures born in the British Isles on the same day as Tom Riddle, implying that she needs one for a ritual to kill Voldemort remotely. Only after the conclusion of an extended search does she explain that finding no such being is a good thing, as if they had existed, the ritual would have killed them as well.
  • Refuge in Audacity: After Umbridge passes an Educational Decree banning teachers from teaching outside of their schedule or curriculum, Hermione points out that classes that aren't accredited by the Ministry don't require a teaching certificate, allowing her to continue the studies with Professor Vector. But when Umbridge finds out, she bans that too.
  • Reverse Polarity: Lampshaded when Hermione visits CERN as part of her research into whether it's possible to transfigure antimatter; they really do use magnetic fields of opposite polarity to slow down charged particles for study.
  • Ritual Magic: Used extensively in the sequel. Hermione uses one to remove the Horcrux in Harry's scar, and in the process makes him and Ginny into Light-aligned Horcruxes. Another ritual is used to kill Voldemort.
  • Rooftop Confrontation: Deconstructed when Hermione fights Bellatrix in the Great Hall rooftop after killing Voldemort for good, she slides down the rooftop, suffering tears in her robes and scraps. It's even given a Lampshade Hanging that rooftop fights are not as easy as in movies.
  • Rules Lawyer: In the sequel, Umbridge and Hermione have this back and forth, with Umbridge having the upper hand because she has the backing of the Ministry.
  • Running Gag:
    • Hermione has a habit of hexing Voldemort and his Death Eaters in the face.
      • Professor Quirrell gets paralysed from behind, where Voldemort's face is stuck on his head.
      • Diary!Riddle gets dazzled by a sunlight charm and his wand snapped.
      • Peter Pettigrew is hexed to pour beetles out of his mouth. And that one was left-handed.
      • Years later, a puppet show for their children, retelling the war, includes a Hermione puppet that faces Volde-puppet and shouts "Hex in the face!" making him fall over.
    • The author notes for each chapter typically include a copyright disclaimer combined with a Shout-Out.
      Disclaimer test number 55: British? No. Female? No. Insanely wealthy? No. Probability of being JK Rowling: 0% within experimental uncertainty.
    • Professor Snape's robes always billow behind him, even when there doesn't seem to be any breeze and it doesn't fit his movement. Hermione suspects some form of magic. When Draco receives the Dark Mark, his robes start billowing too.
  • Run or Die: Confrontation with Voldemort is rightly treated as this by all the main characters. Whenever he takes the field it rapidly becomes a Curbstomp Battle.
  • Science Hero: Hermione and the Twins really enjoy their detailed experiments into how toy wands work (and don't work), and their efforts result in Hermione being able to make backup wands that aren't detectable as underage magic.
  • Shame If Something Happened: As Hermione protests the blood quill detention Umbridge prepared for her, the witch threatens her family because truancy is illegal in the Wizarding World — and the law makes no allowances for expulsion, so Umbridge could throw her out of Hogwarts and then effectively prosecute her (and her parents) for not being there. note 
  • Slowly Slipping Into Evil: Hermione is very concerned that she herself is doing this under the stress of the war, and with good reason. Her brilliance and creativity go in some genuinely evil directions when she doesn't stop herself. Fortunately she has her friends to keep her grounded.
  • Something Only They Would Say: After Hermione suggests that Harry skip a class to prepare for a Triwizard Task, Ginny (jokingly) demands this as proof that she's not an impostor.
    Hermione; When second-order linear partial differential equations are written in four or more dimensions, those with more than one positive and more than one negative characteristic value of the coefficient matrix are classified as ultrahyperbolic.
    George: False alarm. It's her.
  • The Stations of the Canon: Played with, but mostly played straight. All the events of the books occur with only superficial changes. Umbridge is much meaner than in canon, Dumbledore is killed by Draco a few months earlier, the Death Eaters take over the Ministry a few months earlier.
  • Sufficiently Analyzed Magic: It's not entirely there quite yet, but Hermione is on it.
  • Summon Bigger Fish: Hermione lays down the law to the students bullying Luna, by threatening to sic the Weasley Twins on them if the harassment continues. No one wants those two motivated and aimed at them.
  • Super Weapon: Hermione designs one as, essentially, a side project while figuring out how to remove a Horcrux from Harry. It involves runecraft, transmutation, and duplication charms. It couldn't destroy the world... unless you started it in the right place. She is appropriately horrified at what she created, and puts the most important parts of the work under Fidelius.
  • Super Window Jump: During her duel with Bellatrix, Hermione out of a window.
  • Take Our Word for It: Hermione says this to Bill Weasley as she's explaining to him the concept of continental drift, which he finds preposterous.
  • Take That!:
    • The last section of Chapter 68 is one to the Fandom-Specific Plot of magically arranged marriages.
    • Harry and Ginny's second child is named William Kingsley.
      It was certainly better than, oh, Albus or something.
  • Tim Taylor Technology: Wizards believe that Dementors are immune to heat and fire. Hermione takes the view that "if fire didn't destroy it, you haven't used a fire hot enough," and builds a ritual around a solar furnace.
  • That Came Out Wrong: Hermione begs some Pepper-Up Potions from Madam Pomfrey to help her stay awake for 48 hours, and offers to let Madam Pomfrey tie her to the bed and force-feed her a sleeping draught afterward — then realises how that sounds.
  • There Are No Therapists: Averted, Hermione saw a counsellor during the summer after her traumatic experiences in her first year.
  • This Is for Emphasis, Bitch!: Hermione to Umbridge when she has George Weasley attached to a whipping post at the end of fifth year.
  • Torches and Pitchforks: A mob of angry Slytherins run Harry out of Hogwarts in mid-sixth year, as Voldemort consolidates his control over the Ministry.
  • Trauma Button: After her experience in first year, Hermione doesn't cope with the introduction of four security trolls to guard Gryffindor Tower from Sirius Black.
  • Understatement: Hermione learns from Madam Marchbanks that one of the other two geniuses she's tested was Tom Riddle, but Madam Marchbanks doesn't realise who he became.
    Hermione: I met him once or twice...but we didn't get along.
  • The Unpronounceable: Parodied with the infamous Welsh town which Harry, Hermione, George and Ginny visit while on the run from the Death Eater-controlled Ministry.
  • Up to Eleven: Hermione's OWL and NEWT results for Arithmancy are an O*, with explanatory notes that they would award a higher grade than Outstanding if there was one, and that she had the best result since the current version of the exam was created forty years ago. And that they want her to participate in the upcoming review of the exam contents.
  • Walpurgisnacht: The Battle of Hogwarts occurs during this.
  • Voice of the Resistance: In the sequel there are two. Potterwatch on the Wizarding Wireless and the Liberator newspaper.
  • Weak, but Skilled: Quite a bit of Hermione's spell research focuses on making spells efficient, so that teen-agers can fight dragons and Death Eaters. She uses the environment (eg extracting explosive magnesium powder from the soil), targets weaknesses (standard magical shields allow light and sound to pass through), and exploits her medical knowledge to find lethal and nonlethal takedowns with minimal energy requirements. Even first- and second-year students can use her spells to effectively defend themselves.
  • What Have I Done: After their investigations into toy wands result in a homemade model that works approximately as well as store-bought ones, Hermione then realises that she has just given the Twins a way to use underage magic at home.
  • "Where Are They Now?" Epilogue: The Annals of Arithmancy which, while mostly focusing on Hermione, are this.
  • White Magic: Usually especially on the sequel. The horcruxes in Harry and Ginny created accidentally by Hermione and the ritual to kill a dementor in order to restore Luna's soul are good examples of this. However, the text itself refers to the trope by Light Magic.
  • Why Don't You Just Shoot Him?: Subverted; they do try to just shoot Voldemort, with a transfigured sniper rifle. But since he's familiar with muggle weapons he has appropriate protection.
  • A Wizard Did It: Played for Drama regarding Hogwarts' Alien Geometries.
  • Wizards Duel: Several throughout the series, and Hermione spends a lot of time refining her dueling technique and devising strategy. The final battle in particular devolves into one with Hermione, while laboring under a curse that forced her to fight alone. It is appropriately epic, and collapses the Astronomy Tower. It is not with Voldemort, who was killed with ritual magic, but with a grief maddened Bellatrix.
  • You Are Better Than You Think You Are:
    • Hermione points out that while Ron sees himself and his family as normal, not one member of his family doesn't excel at what they do.
    • She has to verbally beat both of her friends into submission to take more advanced classes than the "easy O" classes of Divination and Care of Magical Creatures, pointing out that the two are actually really good at what they do — Harry's mind is fine enough for Arithmancy (with the added benefit of him having muggle schooling, which is better at maths than the wizarding counterpart), and Ron is better at Runes than Hermione is (partly because he loves languages more than she does).
  • You Wouldn't Like Me When I'm Angry: Several characters decide that they do not want Hermione to ever get mad at them.
    • Harry tries out the flashbang spell that Hermione invented in twenty four hours to fight dragons.


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