Petra Njomane/Tropes

== Slytherin ==
* Alpha Bitch: Produces bitchy clique leaders like Gryffindor makes heroes.
* Always Chaotic Evil: Played dead straight for the first five books. Every Slytherin student we see is at least implied to be an elitist, bullying creep concerned with blood supremacy. The password into their common room in Book Two is even "Pureblood." We don't get an actual decent Slytherin until the sixth book, when J. K. Rowling introduced the character of Professor Slughorn — and even he shows some mildly anti-Muggleborn tendencies.
** The only other (comparatively) good Slytherins are bit characters that barely show up in-story. Regulus Black, Sirius's brother, was originally a Death Eater that got the heck out of Dodge once he realized just how evil Voldemort really was and subsequently stole and attempted to destroy one of Voldemort's Horcruxes, but he's long dead by the time the story begins. Andromeda Tonks is a genuinely good person who married a Muggle-born wizard despite being a member of the Noble House of Black, causing her to be disowned and burnt off the Black family tree — and she gets exactly one brief scene in the last book before being mostly forgotten about, her house being All There in the Manual.
** The Cursed Child finally subverts this by providing some unambiguous, purely good Slytherin students with sweet Scorpius Malfoy and heroic Albus Potter.
* Ambition Is Evil: The former Trope Namer. Ambition, as per the Sorting Hat, is the quality that Slytherin supposedly prized among his students alongside purity of blood and cunning. By the time of the series, Slytherin only contains a bunch of pureblood elite Rich Bitch who live on inherited wealth, with very few of them showing genuine ambition.
* Animal Motifs: Sneaky, sneaky Slytherin is associated with sneaky, sneaky snakes.
* Aristocrat Team: The Slytherin House of Hogwarts was founded to house magical students that held the characteristics that Salazar Slytherin valued: cunning, resourcefulness, and ambition. However, due to Salazar's belief that only those of the esteemed wizard families and those of pureblood should be allowed within the halls of Hogwarts, Slytherin House would soon garner a reputation of creating more dark wizards and witches than the other houses. Most of its student body would be from the families of corrupt politicians and aristocrats, harbouring a fanatical Anti-Muggle, Wizard Supremacist ideology that eventually led to the creation of Lord Voldemort and his Death Eaters.
* Barbaric Bully: Slytherin bullies tend to prefer beating the shit out of their victims, their Quidditch team is notoriously brutal, and many of past Slytherin, especially the worst generation from the 60s and 70s, go on to become Death Eaters.
* The Beautiful Elite: When they aren't described as pug-faced and inbred, the Slytherins (usually the leaders) are depicted as gorgeous aristocrats. Averted for the two most prominent Slytherins in the series, Tom Riddle and Severus Snape, who come from poor upbringings which only spur them to be even more ambitious than the spoiled pureblood kids who don't have to study hard to get anywhere.
* Black Sheep: Salazar Slytherin was this to the other Hogwarts founders due to his pureblood supremacist views.
* Black Shirt: A lot of them ended up being Death Eaters.
* Les Collaborateurs: More Slytherins supported Umbridge than anyone else did — though, like Voldemort's case, Umbridge may simply have focused on recruiting followers from her own house. According to Voldemort, a sizable number of Slytherins joined his army in attacking Hogwarts. The rest left with Slughorn and Rowling says that gathered reinforcements from across Britain in support of Harry, though this was never mentioned in the books.
* Color-Coded for Your Convenience: Their heraldic colours are green and silver, meant to represent brackish waters.
* Combat Pragmatist: How they play Quidditch. Rowling also subsequently claimed that they left the school to gather reinforcements during the Battle of Hogwarts, although it was never mentioned in the actual book.
* Cynic–Idealist Duo: The Cynics to Gryffindors Idealist. Most if not all Slytherins, have shown to be untrusting and skeptical of the intentions of others. Snape was perhaps the best example, but largely to how tragic his past was. Narcissa Malfoy was never truly loyal to Voldemort either, because despite his overwhelming power, she cared more for family.
* Dark Is Not Evil: One of the most important things to remember about this house. Though the Death Eaters were mostly Slytherins, not all of them were. There's no doubt, that Slytherin members have done bad things in their histories, but some also did good/right in return. For Slytherin, the ends justify the means, even scum like Lucius Malfoy saw how being a pompous jackass can land you in hot water. Salazar Slytherin himself even warned the other founders, that teaching magic to Muggle-born can be dangerous and at times...he was right.
* Delinquents: Slytherins frequently rely on thuggery and violence to exert influence on other people in Hogwarts.
* Dirty Coward: Self-preservation is one of the traits of Slytherin; while this doesn't always translate into cowardice,note  it often does for Slytherins that aren't on the side of the bad guys.
* Dumb Muscle: Despite being described as cunning, witty, and ambitious, most Slytherins fit this trope, i.e. Crabbe, Goyle, and just about the entire Slytherin Quidditch team.
* Dysfunction Junction: Slytherins, especially during Harry's school time, are frequently the children of snooty high society types, Death Eaters, psychos, murderers, and/or all of the above and many of them seem to have inherited their parents' prejudices and then you get the occasional half-blood in the house like Millicent and Tom Riddle—it's like blood in the water.
* Elaborate Underground Base:
** The Slytherin Common Room is located in the dungeons. It adjoins the Great Lake, giving it a greenish tint.
** The Chamber of Secrets, accessible only by the Heir of Slytherin, is similarly located under Hogwarts.
* Enforced Cold War: With Gryffindor.
* Everyone Has Standards:
** Beyond Pansy Parkinson, none of the Slytherins seem to want to sell Harry to Voldemort in the Battle of Hogwarts.note
** In the film version of Order of the Phoenix, a few Slytherin students can be seen cheering the Weasley twins after they wreck Umbridge's classroom, implying that even they don't like her.
* Evil Reactionary: Pure-blood supremacist ideas are a core of Slytherin's history, and it has resulted in the decay of the house, in Harry's times, into a cesspool of elitism, bigotry, and general social regression.
* Fantastic Racism: Many Slytherin characters we are introduced to have serious Pureblood biases. Hell, their Common Room's entry password is "Pureblood", inviting questions whether the house even accepts Muggleborns at all. We know that it at least accepts Half-bloods like Tom Riddle and Severus Snape, though.
* Fatal Flaw: Slytherins often lack the scruples to counteract their ambition, leading to ruthlessness and prejudice. Elitism is also a common issue for them.
* Flanderization:
** It's likely that Slytherin suffered an internalized version of this as a result of Voldemort's rise to power. The only major Slytherin free of interest in the Dark Arts and Blood Purity is Horace Slughorn, who comes from an earlier generation than Voldemort. Basically, Voldemort's obsession with being the Heir of Slytherin and the fact that he recruited Death Eaters from his own house and then their children after them, essentially cast a large blot on their legacy, making people believe that their extreme aspects were their core ideas.
** As a Slytherin, Slughorn prizes reaching the maximum potential of your talent and the social impact and benefit it can have on the rest of the world, showing a commitment and interest in the bigger picture that other houses often lack and ironically doing more to encourage mixing of houses and building house unity than even a model of fair play like Professor McGonagall.
* For the Evulz: What the worst of them lapse into, even if it's technically not their credo.
* Four-Element Ensemble: Represents Water among the four Houses, reflected by their most prominent staff member, Severus Snape, who brews potions, and their common room, which is under the lake.
* Gondor Calls for Aid: While they were the only house that leave the castle en masse during the Battle of Hogwarts (see below), Slytherins did return to help Hogwartsnote  when everything started going to shit for Voldemort and the Death Eaters — although you'd never know that from reading the books, as Rowling only mentioned this later.
* Greater-Scope Villain: Salazar Slytherin, being the founder of pure-blood supremacist thought which drives most of the major villains.
* Green and Mean: Their house colours are green and silver. The Slytherin Common Room is also depicted as having a constant greenish tint, because it's located underground, adjoining the Great Lake.
* Hate Sink: In the first five books, all named Slytherin students that Harry meets are described as rude, racist, elitist bullies and cowards with no redeeming features or members whatsoever. To top it off, most are described as dumb and ugly, though this can be attributed to Harry being an Unreliable Narrator.
* Informed Attribute: The Hat of Slytherin house, we are told, is ambition, but with the exceptions of Snape and Tom Riddle (which are ironically half-bloods, far from the Slytherin paragon), no one we see in Slytherin displays any genuine ambition. Slytherins are likewise supposed to be cunning, witty, and defenders of "wizarding pride," but most of the canon Slytherins are bullies and Dumb Muscle who enjoy more physical presence than wizarding talent, and whose idea of "cunning" is openly attacking Gryffindor Quidditch players before a game and then banking on their Head of House to bail them out. Then again, with no ambition to put as a hat, they are left with racism or being deceptive, which aren't values for a school to have. Presumably, most of them are in there because that's the House they wanted to be put in.
* It's All About Me: A common trait and flaw of the Slytherin. They often do their deeds thinking of themselves and not others.
* Jerkass: Pretty much all named Slytherins in the main series are assholes, except Slughorn, Andromeda Tonks, and possibly Regulus Black.
* Jerk Jock: Slytherin's Quidditch players are often shown to be one of these. Higgs and Pucey are notable exceptions.
* Motive Decay: It’s implied the whole house has undergone this over the centuries, having once produced great wizards such as Merlin that avert Ambition Is Evil by seeking to bring positive change to the wizarding world. Now, the house is almost all snobbish aristocrats pushing traditionist wizarding values of blood purity.
* My Species Doth Protest Too Much: What few Slytherins aren't complete jerks are this and can be quite amicable as Slughorn can attest.
* Neutral No Longer: It's implied that the majority of Slytherin simply didn't pick sides in the war, probably due to their house's enmity with the other three leaving them no safe haven if they sided against Voldemort and the children of his supporters decided to get revenge. But when push came to shove and it was clear that Voldemort was going to take or lose everything, the Slytherins spread out across Britain to gather up just everyone they could find to help fight, and then returned with an army that could win purely through virtue of numbers — or so Rowling claimed in a interview later, the actual book has Slytherian House evacuated en masse after one of their number tries to turn Harry in to Voldemort. They're never spoken of again afterwards.
* Never Be a Hero: Their trait of self-preservation manifests as this trope. While Slytherins are unlikely to perform the heroic feats of Gryffindor, they're also less likely to needlessly endanger themselves as a Gryffindor would.
* Noble Demon: Though the Slytherin house's reputation for cruelty and selfishness is well deserved (and well-earned), to the few people whom they deem worthy of their love (or at the very least, respect) Slytherin are capable of loyalty, bravery, honor, love, kindness, and heroism fierce enough to equal (and sometimes even rival) any Gryffindor. Of course, they are not the majority, most of them genuinely live up to the worst of their House reputation.
* Obviously Evil: Their emblem is a snake, they live in a dungeon, part of their folklore concerns their founder, who only wanted to teach pureblood, leaving a monster to "cleanse" Hogwarts of undesirables, and they are a group that extols underhandedness, self-centred behaviour, exclusivity, and at various points in history, outright bigotry. Oh, and it was the training ground for the vast majority of the 20th Century's dark wizards. Working around the house's unpleasant image was an uphill battle, both for the fandom and for Rowling.
* Offscreen Moment of Awesome: The Neutral No Longer / Gondor Calls for Aid. It would be great if we actually got to see that happen; instead it's just a vague "Hey look! reinforcements!" moment. Then Rowling confirms in an interview that the Slytherins came through for the good guys, and probably because they realized that the situation was dire and some things were more important than their prejudices.
* Planet of Hats: Until the sixth book, all Slytherins seen in the series are depicted as unpleasant people. They are either bullies, blood supremacists, or both.
* The Spock: Slytherins are defined by their ruthless pragmatism and self-preservation. While this doesn't make the house inherently evil, in spite of its Motive Decay, it's hard-pressed to produce heroes as Gryffindor does.
* Token Good Teammate: A small example, but Harry notes that two Quidditch players, Adrian Pucey and Terence Higgs, are genuinely good opponents who don't have a long record of fouls and cheats behind their names. Higgs is replaced by Malfoy after the first book while Pucey keeps fulfilling this role in the Quidditch team up until the third book, where he's replaced with Warrington who is more aggressive and underhanded. However, he returned for the fifth book.
* The Unfettered: With ambition and pragmatism being two of their greatest traits, Slytherins will "use any means to achieve their ends".
* Upper-Class Twit: Mostly those from Draco's year or social circle. Crabbe, Goyle, Pansy, Flint, Bulstrode, and Pike are all shown to be not very bright or outright unfriendly to the others.
* The Usual Adversaries: Most Death Eaters were educated at Hogwarts, and with two known exceptions, every last one of those was a Slytherin.
* Villain with Good Publicity: Slytherins are stereotyped as "evil" wizards, yet the actually evil ones seem to have both an unusually high amount of followers and disproportionately large representation in the wizarding government.
* Wicked Cultured: An article on Pottermore has been written on the various treasures owned by Slytherins, stating that they had "displayed some exquisitely dark, yet beautiful designs over the years". This is most apparent in their common room, with its dim green lighting, skull decor, black leather furniture, and views of Hogwarts Lake from beneath the surface. "Say what you like about Slytherin house, they had great taste."