Knights of Cerebus in fanfiction.
- Gilda's initial appearance in Ace Combat: The Equestrian War ends with her breaking Medley's wings and causing a Heroic BSoD to Rainbow Dash.
- A few chapters earlier, Black Star. When he stated that only Firefly was able to fight him equaly, he wasn't making it up.
- Advice and Trust: Once again, Bardiel fills this role. The story's tone takes a much more serious and drama-focused weight during and after the battle, with Hikari left disembodied inside Unit-03 as well as Shinji and Asuka being thrown into solitary confinement.
- All For Luz, Antagonistic Governor Rodger Maxwell the first Arc Villain is the mastermind behind the Death Camp intent on killing the 33 kids just because they had superpowers and ultimately responsible for many of their fates. His machinimas continue to haunt Luz long after his arrest and imprisonment.
- The Ask Princess Molestia
blog is typically about the wacky and lighthearted hijinks of a Memetic Molester and an endearingly dorky Gamer Chick. However, whenever Fausticorn swings by for a visit, it careens into a rather dark and depressing drama that shows Molestia has some serious issues. Give it a few posts and it's back to normal, but after that first visit, things never quite made it back to the original silliness. - Avengers: Infinite Wars:
- First of all, there is Durge, a Psycho for Hire One-Man Army hired by Dooku specifically to deal with the Avengers. The mercenary is nothing but a sadistic and unstoppable monster, capable of mowing down true clone troopers as if they were made of paper and every time he shows up, people die by the dozens.
- Ultron. While at first the genocidal A.I. decides to take his time and acts from the shadows, the very moment Ultron makes his grand debut in Chapter 47 by attacking not only Coruscant, but every major location important to factions of the conflict, everything goes to hell, with the villain scoring victories and forcing all sides into a corner over and over again. By the time the Citadel arc and his depraved Assimilation Plot is exposed, Ultron has officially surpassed both the Separatists and Sith as a threat not only to the Galaxy Far, Far Away, but to all life in the universe, forcing all sides to a truce.
- The Son/Lord Bogan. After escaping his canonical death in Mortis, the embodiment of the Dark Side causes the story take an even bigger turn for the worst by taking control of the True Sith faction and helping the Darksiders bring some of the most powerful and dreaded Sith Lords back to life, throwing the Galaxy in even more chaos than Ultron did before him.
- And of course, Thanos, who hasn't even physically appeared in the story yet, but whose sheer presence through Maul (himself already a major example of this trope) indicates he will bring the story to its Darkest Hour.
- Happens twice in Calvin & Hobbes: The Series to indicate that Cerebus Syndrome is kicking in harder:
- Dr. Thunderstorm and Shadow, the villains of season 3 finale "Thunderstorm", are shown to be the most competent threats the series has had thus far, actually managing to Take Over the World and destroy the MTM. It takes a lot to defeat them.
- The season 5 (and series) finale "Black Rain" abruptly introduces the Slender Man of all people, and his appearance is a haunting as always - especially when he "kills" Thunderstorm and Shadow at the end.
- The arrival of the Benefactor's disciples in Challenge of the Super Friends: The End.
- Child of the Storm:
- The first few chapters, while good in their own right, were mainly just about Harry reconnecting with his dad, who was revealed to be Thor, and bonding with the Avengers. However, the moment the Winter Soldier comes on the scene and starts wreaking havoc is when the tone starts to shift.
- Gravemoss' actions in chapter 21 cement the darker turn and take it even further.
- Voldemort is this for Book 2, Ghosts of the Past. The tone was light and almost sitcom-esque until he showed up, at which point it becomes very dark.
- Children of Remnant:
- As a general rule, any time that Salem gets mentioned, the humor in the story evaporates and it takes a long time for it to return.
- Once Marcus Black enters the narrative, it gets a lot more serious in a manner that never disappears, as Marcus is the assassin the conspiracy hires to kill Jaune.
- Professor Moriarty in the first finale of Children of Time. There have been a lot of monstrous beings and despicable actions to date, but no one with as thorough a vendetta against Sherlock Holmes as the Professor. Notably, within 5,000 words of his introduction, the whole world basically goes to hell.
- Cinders and Ashes: the Chronicles of Kamen Rider Dante has Magane as one. While she is one in her anime, this fanfic has her take her role and run with it. Her cameo signals the shift to a darker and more serious tone, with the following scenes featuring her as a major threat, to the point where her first encounter with Hoshi brings with it his brief Face–Heel Turn. While an honorable mention goes to Vega for bringing the Kaizo-Majin into the world and Malacoda for almost killing Hoshi's sister, Magane is the one who, directly or indirectly, is responsible for the more reprehensible Kaizo-Majin that managed to score more kills than the Kaizo-Majin that Vega makes.
- Citadel of the Heart has at least one being introduced beginning in the Chapters 12-14 range in every installment of the series, as acknowledged by the continuity's very first Knight of Cerebus from Truth and Ideals as detailed below:
- Truth and Ideals: Regulus is a nicknamed Lucario having originally been owned by Ash's Disappeared Dad when he was just a Riolu, and when we first actually get to see him, he casually reveals more information about Ash's past as well as showing possession of a Lucarionite Mega Stone, and his debut ends up leaving Ash comatose for a few days on end because of Regulus not knowing his own strength.
- Sword Art Online: Special Edition: Grandis, the primary Author Avatar of the entire continuity, is introduced in a fashion that answers many questions as to where Chronicler came from and why he has his distinct powers, but most importantly opens up a whole new can of worms in the fact Chronicler is only half of what Grandis himself is 100% of. What little we see of Grandis showcases him to not only be a far stronger opponent than Chronicler could ever be, but also the fact Grandis is restraining all of his abilities and frustrations to the point nobody has a clue as to how to handle him, yet alone as to how to handle his backstory of how he first arrived on this Earth.
- Code Prime: While certain antagonists like Starscream and even Megatron are undoubtedly evil, they still manage balance some levity from time to time. The characters below, not at all.
- Airachnid, per canon. From the moment she arrives in the story, all of her actions Played for Horror, and the author doesn't shy away from her character's brutality.
- V.V., while portrayed a Big Bad Wannabe that is always underestimating those around him, is still just as, and eventually more, vile than his canon counterpart.
- Shin Hyuga Shaing, is another example of it. An Omnicidal Maniac that thrieves with the misery of others, specially his brother Akito, Shin is one of the most despicable and dreaded antagonists in the story that always makes things take a turn for the worse.
- And finally, Unicron, who hasn't even appeared in the story as of R2, but whose simple mention is enough to strike fear into does so. Of course, anyone remotely familliar with the Transformers lore knows it is only a matter of time until the Chaos Bringer makes himself known and then all Hell will break loose. Alongside the Cybertronian God of Evil as threat that has yet to fully reveal itself is Beleth, the first bearer of Evil Geass, who is pretty much The Antichrist of this world, and directly responsible for the creation of Dark Geass, a malicious ability that only serves to bring pain and despair to those it is inflicted upon.
- Common Sense makes the Trope Namer Terrible Trio of Team Rocket into one of these, with a severe increase in competency and a large amount of collateral damage (mostly by invoking The Bad Guy Wins on several heists that they didn't pull off in canon) in their unrelenting chase for Ash's Pikachu that is slowly turning the Pokemon trainer's Chronic Hero Syndrome into a full-blown martyr complex (because as he sees it he's The Only One that seems to be doing some kind of damage to their operations, and he's still losing badly). Doesn't helps any that in time TR actually starts to invoke the Worthy Opponent card on Ash... mostly as a way to Draw Aggro so he can't help people.
- The Contractually Obligated Chaos series has thus far introduced two. The first is Erebos, Arc Villain of the second story; he's a Living Shadow whose main scheme for weakening his victims is to Break Them by Talking until they make a Deal with the Devil. Even worse is Vasile, in the third story, a specific type of murderous poltergeist who feeds on children.
- A Clash Of Neets: While the story has its share of legitimately serious villains, they tend to be either Laughably Evil (The Lord of Light an his followers) or The Comically Serious (Stannis, Baelish). However, the Great Other, also known as the Kinslayer, real name Arthas Menethil, is the exception: whenever he appears in a chapter, all comedy and lightheartedness immediately stop, and the tone turns dead serious, as heroes die and the shere horror of what the Children of Destiny are up against is displayed. There is nothing funny about him.
- As soon as Beyond Birthday shows up in Constant Temptation things get really dark, really fast. He's somehow made even scarier than he is in canon.
- Danny Phantom: Stranded: While Colette Bevier has some comical moments, like when karma catches up to her, they do nothing to detract from the fact she's a rotten Spoiled Brat who has made it a hobby to make her stepsister Star miserable just for laughs since the minute they met through bullying her or stealing her boyfriends. Danny being the only exception has turned Colette into a Stalker with a Crush toward him. She's at her worst in "Empowered", where she gets ghost powers and plots to take over the world, destroy Star, and make Danny her's by force, and "Blackmailed", where she's willing to ruin Team Phantom's lives by framing them for crimes and blackmail Danny into dating her and emancipating himself from his family.
- The Dark Side of the Mirror Verse:
- Mirror!Spitfire. While there are some serious moments, anything dealing with her is treated seriously, and Rainbow Crash is absolutely terrified of her. For good reason, as her abuse left her the broken wreck she is now, and she's also responsible for Fluttershy's Bystander Syndrome. Not to mention that she's The Quisling and willingly sided with Mirror Celestia to help destroy Cloudsdale.
- Twilight's Superpowered Evil Side, Nightmare Spotlight, who while not as vile as the above, makes up for it in sheer threat level and the confrontation with her has much higher stakes than the rest of the story. She puts Trixie in a Deadly Game, nearly freezes her solid, almost kills her and Maud, and comes very close to destroying Canterlot.
- Diary of an Analog: Machinedramon is given a major case of a Cerebus Retcon regarding his origins, being depicted as not only the Dark Masters individual we know him as from Digimon Adventure, but he's also the exact same Machinedramon from which Analogman had used in Digimon World. Machinedramon, even though his remains have been rendered into a self-repairing sack of spare parts, even when currently helpless, Machinedramon is the one bullying the strings behind his figurative and literal dragon that is Darkdramon and the D-Brigade, from which Machinedramon is to Piedmon as Darkdramon is to Myotismon in the fact Machinedramon had created Darkdramon as a Digimon of free will who he would use as his Puppet King for his new incarnation of the Dark Masters from whom Darkdramon will serve as his enforcer once his training is complete, even when it becomes aware that Darkdramon's free will gives him more than an agenda of his own accord, such as starting off his villainous deeds by agreeing to an anonymous bounty on Sora's head placed on her in the wake of Y2K, and then proceeding to toy with his food by outright making Sora's waking life nothing short of a living hell for her in the following years.
- Denkuma in Volume I of Dragon Ball X. Up until then the series had a very "villain of the week" sort of style, usually ending with the acquisition of a Dragon Ball. Even Porter and Cuo, while dangerous villains, weren't overly threatening and were dealt with without much collateral damage. Cue Denkuma. His debut had him absolutely destroying and humiliating the main characters in battle, and a chapter or two later it's made very clear exactly how dangerous he really is. The rest of the series immediately took a turn for the dark that didn't ease up until the last half of the final chapter of Volume I.
- In The Dresden Fillies, the story takes a darker turn when Trixie and the Nightmare kidnap Spike.
- Dungeon Keeper Ami: a strange, strange example in the form of Mukrezar. Mukrezar is a goofy, slightly manic Keeper of dubious competence. He doesn't even look threatening, he's a pink-haired elf! Following his resurrection he serves as a decidedly plucky comic relief sub-plot and foil to Ami's introverted competence. Yet despite all of this, the story has not only arguably taken a turn for the darker since his introduction, but the level of threat posed by Mukrezar has risen exponentially with his every appearance. Why? Despite dubious success in most of his Zany Scheme -ness, his sadistic streak and ability to bounce back from crushing defeat is intimidating to the extreme.
- Earth and Sky: A mild example, all things considered, but Diamond Tiara's entrance into the story (followed shortly after by the Flim-Flams) not only brought in actual antagonists, but also an overall darker tone to the story.
- Subverted with Chrysalis. At first it looked like she was going to be a Knight, but instead was reduced to an Ineffectual Sympathetic Villain, whose one major act of villainy (framing Rarity being a changeling) was negated within hours.
- Equestria Girls: A Fairly Odd Friendship: The story, while somewhat more dramatic, is a mostly lighthearted fare. Then the Dazzlings move into the picture, and while they do have humorous moments, their villainous actions are not Played for Laughs. They destroy Sunset's relationship with Timmy by exposing her horrible past to him and feeding him a dark untruth that she is planning to steal his fairies, which leads to Timmy turning Sunset into a worm. They then proceed to manipulate and abuse Timmy into granting their wishes. Then, after they manage to enthrall Cosmo and Wanda and take their magic, they brainwash Timmy's friends and family into hating him, and manipulate him into trying to kill the rest of the Rainbooms. And then when Timmy mouths off to them, they subject him to a horrific No-Holds-Barred Beatdown, and threaten to throw Trixie off the roof if he doesn't grant their wish to rule Dimmsdale.
- Equestria's First Human was already dramatic, with Connor's social isolation from Ponyville, and the Mane 6's own social isolation for relating to him. Then comes Hellfire, a unicorn stallion with a crazed vendetta against Princess Celestia. His first act on screen was to mutilate one of his subordinates for failing a petty order.
- The Equestrian Wind Mage has Dethl, oh so much. While Season 1 is primarily Slice of Life, his presence immediately makes things deathly serious — he possesses Diamond Tiara and uses her to try and kill the Cutie Mark Crusaders, in order to hurt Vaati (who had adopted Scootaloo), for no reason than anger at Vaati's Heel–Face Turn. When the plot fails, he leaves the disoriented Diamond to get arrested and sentenced to Tartarus, where she tries to commit suicide by monster, only to fail and get turned into one... at which point, Dethl possesses her again in another attempt to kill Vaati's friends. And this is all before we even know who he is. And the reveal of his identity, and his connection to the Church of Majora, in the season finale just opens the path for the Cerebus Syndrome that the next two seasons suffer from.
- Ghirahim is this for the episode that focuses on Daring Do. He shows up out of the blue and offers the power of Majora's Mask to Ahuizotl. Daring Do, naturally, attempts to steal it from them, but Majora promptly trips her up, allowing Ghirahim to corner her and beat the ever-loving snot out of her, only being saved by Ahuizotl's intervention. Ghirahim later visits Daring in the dungeons and proceeds to torture her, and is explicitly stated to be sexually aroused by her pain! His presence ultimately ends Daring and Ahuizotl's semi-playful rivalry.
- Freakin Gensokyo: Matt, the main character's friend, sees Gensokyo as little more than a playground for murdering people with scissors. It is played either for laughs or neutrally to begin with, right up until the reveal that Matt murdered Maria's mother.
- Getting Back on Your Hooves had some sad moments in the beginning, but mostly a rather lighthearted story about Trixie trying to do exactly what the title says...Then Checker Monarch enters the picture. Word of God states her mannerisms were based off those of a sociopath if that's any indication. Example? She Mind Raped Rainbow Dash and convinced the Diamond Dogs not to try anything funny with her by saying she'd turn their mine into a parking lot...with them under it. That was only her second appearance.
- Haunted Mansion and the Hatbox Ghost: While the backstories can be pretty dark, "present-day" shenanigans taking place when the cast had already left their corruptible mortal states are usually fun and games. Not so whenever the One-Eyed Black Cat is present, however.
- The Vocaloid fanfiction Hear my Song! has IA. She's first introduced as an Korean Idol Singer who Miku listens to on the radio, and then as Yukari's Stalker with a Crush. And then she breaks SeeU.
- Heroes Never Die It's Hero Time: While All for One remains as much of threat as he is in canon, Vilgax, being the Crossover Villain-in-Chief takes this role. His status as The Dreaded makes any lightheartedness in the story go away simply by being mentioned, and then he officially makes his debut in Chapter 83, delivering a massive Gut Punch against the characters following All for One's defeat in Kamino, brutally killing several Red Shirt characters before taking All Might away with him.
- History's Strongest Shinobi: Neji. He's basically only in town to kill Naruto. This immediately raises red flags for everyone (our heroes and Ragnarok) as preceding this, the worst that could happen to someone in their fights was getting sent to the hospital.
- How Trixie (Somehow) Saved Hearth's Warming has the Big Bad Leidr. While the secondary villain the Rat King isn't a push over and quite dangerous, he's still a Large Ham and his lair has many comical quarks. Leidr serious and when the confrontation with him takes place, the tone becomes much more serious and most of it is a Curbstomp Battle in his favor. He's also a very powerful sapient Windigo and carries all their frightening attributes. According to Word of God, this was based off of how some Christmas Specials (which the story is a Homage to) had surprisingly frightening villains.
- I Against I, Me Against You: Wyoming of all people ends up becoming this. Although the Freelancer himself is about as much of a threat as he usually is, he sets off the more serious story of Twilight's arc in Act 1 when he makes her a priority target for Project Freelancer, and is the first human Twilight meets who seems to know about Equestria.
- Then there's the Meta who massacres the entire Equestrian military contingent around Tex's ship, as well as a significant amount of ponies in the nearby town. To say that things immediately get more grim afterward is an understatement.
- Ignited Spark, The Villain Consortium, led by Nine and his crew. The first 13 chapters of the story are relatively lighthearted, even if a bit angsty at some points, but still with plenty upbeat. Until they showed up during the USJ. And then the arc develops into something straight out of horror story, with the main characters almost dying in the process.
- Intercom is an Inside Out fic, and its Knight of Cerebus is Tracy. A school bully, her accusations towards Riley about a stealthy reference to having emotions in her head begins creating drama for Riley and the emotions that will have repercussions for the rest of the fic.
- Invader Zim: A Bad Thing Never Ends: In a story where even psychopaths like Zim or Aldrich Coathanger are played more for Black Comedy than anything else, Lex is the one antagonist played deadly serious, being a No-Nonsense Nemesis fully capable of overpowering and mind raping his opponents thanks to his Brother.
- Jaune Arc, Lord of Hunger:
- While not without drama, the story starts out fairly lighthearted and is about a Force-sensitive teenage boy learning to master his powers as he settles in at his new school. That all changes with the introduction of the terentatek—a homicidal alien beast mutated by the Dark Side and hellbent on tearing Jaune apart limb from limb. For Teams JNPR and RWBY, the terentatek is the first serious threat they've encountered that outclasses them in almost every way and who Jaune's Force powers don't work on. The battle between the heroes and the terentatek is noticeably Bloodier and Gorier than any of the fights preceding it with limbs being broken, a teenager getting disemboweled, and the main protagonist almost dying in a pool of his own blood. If it wasn't for a last-minute Gunship Rescue, the entire main cast would've died then and there. In addition, the terentatek's debut marks the start of Jaune's Protagonist Journey to Villain as he slowly becomes corrupted by the Dark Side in later chapters.
- All that above pales in comparison to the dark, inescapable horror that is Darth Nihilus. Whereas even Cinder had her humorous moments, nothing about Nihilus is ever Played for Laughs. He's an insidious Omnicidal Maniac whose corruptive influence on Jaune is one-hundred percent Played for Drama as it drives a wedge between Jaune and his friends while pushing him ever closer to a Face–Heel Turn. Nihilus' inclusion in the plot is directly responsible for the fic being Darker and Edgier than its source material, with chapters featuring Nihilus as a POV character being among the darkest in the entire story. Once he possesses Jaune's body and takes an active role as the Big Bad, the story dives headfirst into the Cerebus Syndrome with Characters Dropping Like Flies as over a dozen heroes and villains alike are Killed Of For Real by Nihilus' rampage.
- The Geeky Zoologist's reimagining of Jurassic World has two main ones:
- Once the Indominus is introduced, the story starts to deal with the darker aspects behind the fantasy of the park and by the end of the scene in the Coliseum, the reader knows that it’s only a matter of time before things goes south because of her.
- The group of mercenaries who have staged the Indominus’ ambush on Brunet’s platoon and murdered Gareth Turner, Mei Tian and Patience Bellamy, darkens the story’s atmosphere even more. When the grey guards discovers that this group of mercenaries is actually InGen’s black ops team, things escalate and a war break out on the island between InGen and the Grey Guard.
- RWBY fanfic series, The Makings of Team CRME:
- The darkest story in the series is The Black Hearts. And a big reason for that is the inclusion of Mercury Black's parents, Marcus and Melanie. While things weren't exactly sunshine and rainbows, their inclusion really brings down the tone in Mercury's story. Even Brigit Stark from My Name Is Cinder doesn't make things as serious as Mercury's story and she is killed two chapters into the story. And the antagonists from the other stories (as ruthless as they are, still have sarcastic jokes to lighten the mood. Mercury's story is nothing more than him enduring the Domestic Abuse at the hands of his parents, made even worse by the fact that Marcus is an alcoholic, sadistic assassin, making him more unstable than Brigit was. And even though Melanie is an abused spouse, she does not garner much sympathy either since she still verbally abuses Mercury, doesn’t even care much about his well-being, and continuously cheats on Marcus. If not for Mercury's humor, the story would be even more depressing than it already is. And he is the only protagonist suffer to suffer serious, life-long injuries at the end of the series. The ending of his story is the most depressing one in the series and would be a Downer Ending if Cinder and Emerald hadn't showed up to save him from dying of blood loss. And Melanie's appearance in CRME results in one of the darkest moments in that fic so far. She triggers Cinder into committing a brutal act of violence that exposes how deranged she is underneath all her elegance.
- Mercury himself also has this effect on Cinder and Emerald's relationship in CRME. Him joining their team makes Emerald jealous and concerned about being replaced and this causes Cinder to start abusing her when she thinks Emerald is being too defiant. And Mercury starts attempting to expose the true nature of Cinder's view of her as nothing more than a tool.
- Despite its cynical tone, Miraculous: The Phoenix Rises most of the time keeps to following the main characters goofy hijinks surrounded by episodes of Black Comedy. However, when any mention is made of the thug who framed Morgan for stalking, all of that vanishes.
- Shared with Dr. Nicole Cho, the abusive school counselor.
- Mischief (MHA): In true Marvel fashion, Ultron. From the moment the villainous A.I. is mentioned back in chapter 48, all lightheartdness of the story gradually falls down until it disappears completely during the I-Island arc. To immeadiatly establish himself as threat like no other the story presented so far, brainwashes Wolfram, kills Sam and all the Brotherhood mercenaries at the Expo in the most brutal and bloody way possible before setting off to enact a genocidal scheme to destroy humanity. By the end of the arc, not only he is the first major villain (besides Loki), to effectively defeat the Heroes, he is still loose on the world, and about to join the Villain Team-Up with Loki and Thanos.
- In My Little Denarians, the Denarians. Discord may be more powerful, but the Denarians are more evil.
- My Little Pony: The Mentally Advanced Series:
- The Monster from Rainbow Dash Presents: The Haunting. While The Abridged Series has always been chalk full dark and even depressing elements, as you would be expected in a Crapsaccharine World version of Equestria, ruled by an insane Evil God, with a secret war being fought by Eldritch Abominations and a cynical atmosphere, they had always been Played for Laughs. Until this guy showed up and Mind Raped Twilight into helping it try to devour a couple of the characters, while singing its surprisingly menacing Villain Song "Bones and Skin".
- Likewise, when Twilight starts hallucinating Yellow Star in RDP: The Star In Yellow, the story starts shifting from Comedic Sociopathy to Cosmic Horror Story.
- In canon and Neon Metathesis Evangelion alike, Bardiel fulfils that role. Whereas most angel battles before are relatively easy, Bardiel requires Rei to sacrifice herself. And afterwards, the tone is somewhat darker.
- The New Adventures of Invader Zim has Norlock, the vampire who ends up serving as Zim's Dragon-in-Chief. While Affably Evil, he's a No-Nonsense Nemesis who is by far the most dangerous character in the setting, and his mentoring drives Zim to become even more of a threat than he already is. And he ends up serving as the first season's Final Boss after he ultimately betrays Zim.
- There's an amusing attempt to invoke this in A New Order. Nephrite proves himself to be frighteningly competent very quickly, his first appearance resulting in the first innocent deaths of the story. When he first shows up, he's accompanied by a three-headed wolf youma named Kerberos. Word of God is that this is because the author thought the trope was Knight of Cerberus, as in the 3-headed hellhound, and wanted to invoke it.
- Old West was never clean of blood to begin with, but it becomes more serious by the small role played by Benjamin Hares, Grace Glossy's estranged traitor of a husband. The chapter where he subjects Grace to domestic violence is one of the darkest moments of the story. Though Grace's lover Rattlesnake Jake gives Benjamin his comeuppance (a painful death through a venomous bite), Grace's sense of self-worth is destroyed for the following chapters, putting her previously good relationship with Jake on a strain. Also, Benjamin was brought in by Dufayel to legally claim the ownership of Grace's property. Benjamin's failure is the last straw for Dufayel who finally decides to stop playing by the law and use more drastic measures against the heroes.
- Saint Ayame and Saint Sarutobi from One Piece: Parallel Works. We first see them trying to enslave an entire island, which Aria talks them out of. But, as the series progresses, we learn that they've done some pretty nasty stuff, especailly to Heathcliffe and Yuki-Rin. Kicking Heathcliffe out of his house and killing Molly's parents ( even though her parents faked their deaths) don't even begin to describe how they've also almost brainwashed Holden by sending him to a boarding school for the children of the Tenryuubito. It's also implied that Saint Ayame frequently beat Yuki-Rin for her love of pirates.
- One step backwards and Three forwards has G, aka Giulietti. A criminal mastermind who takes an interest in Alya's supernatural sleuthing abilities, he offers to recruit her in order to deal with Paris' nascent superhero problem. His involvement helps steer the series in an ever darker direction, as Alya takes him up on his offer, with the bodies starting to pile up.
- In The Parselmouth of Gryffindor, Barty Crouch Jr. plays this role. Pre-Crouch plot: no villain, Voldemort is a silver monkey, fun and good times. Post-Crouch plot: Inferi and Hermione is dying. Notice anything? Not that a good dose of wacky humor doesn't remain throughout, but the stakes have definitely been raised there.
- The Acromantula Army's attack is portrayed much more seriously than most other events in the story as well, and is the only time someone dies in the story so far, although only nameless Red Shirts.
- In Perfection Is Overrated:
- Hitomi Kirihara is the first SUE with hostile intentions toward the Himes, and abuses her Mind Control powers to rob and murder people. Over 20 people end up dead as a result of her actions, and this turn of events causes Nao to agree to cooperate with the Himes in spite of being reluctant to do so.
- Bachiko and Meiko present more of a threat to the Himes than most of the SUEs, setting them against each other and playing into the canon antagonists' plans. By the end of Chapter 19, Yukariko and Ishigami are dead, Mai barely avoided causing Yuuichi's death while surviving an attack from Shiho, Natsuki had to protect Nao from Shizuru (and then Shizuru from Nao), and Bachiko and Meiko are finished off by a Brainwashed Mikoto.
- Even though Phineas and Ferb Visit Jurassic World! is a Lighter and Softer take on the film, the Indominus rex is still played quite seriously. Things immediately turn dark the moment she shows up, and everyone in the cast labels her as The Dreaded upon encountering her. Even Perry the Platypus finds her terrifying. She even still manages to cause one death.
- Pokemon Mystery Dungeon Hope and Faith Saga starts getting ugly once Unod the World Destroyer appears.
- Chapter 22 of Pokémon Reset Bloodlines introduces Belladonna Tyrian, who by Chapter 23 really shows herself as this trope. Even with it being well shown that she's not tied to or even aligned with the story's more overarching antagonists, like the Bloodline King or MissingNo, she still becomes the first villain in the main story to kill someone on screen as part of a ploy to kill the abusive father of one of her lovers without putting the rest of their lives in direct risk. The scenes with her are so dark that during her entire conversation with a captured Ash, Dexter, who is generally shown to be constantly snarking at everything, is uncharacteristically silent. She also turns Pokemon's, both the original series and the fics, Identical Stranger trope on its head, suggesting that it is in fact another trope entirely: Long-Lost Relative. Notably, it's only after she appears that the fic finally reveals the Reset verse's version of Sabrina, and in the side stories Capriccio.
- Pony POV Series
- Loneliness; up till she showed up, the Reharmonization series was much more light hearted than the Discorded Ponies series — it had its dark moments, yes, but nowhere near the amount of horror Loneliness brought with her. Not only that, but only a couple of chapters later the Princess Gaia arc started up.
- Shining Armor's arc has General-Admiral Makarov. Things take a turn for the serious when he shows up, whereas before it was all pretty lighthearted minus an early appearance by the Stalker. And then even more so once we find out he's an Equineoid Abomination who only Shining may be able to defeat.
- Nightmare Eclipse/Paradox manages to be this for Dark World, which was already Darker and Edgier. When the story finally turns to her, it instantly becomes a Wham Arc and the stakes go simply from freeing the world from Discord's tyranny, to having to save the entire timeline from being erased from existence due to her "Groundhog Day" Loop plan. Add in her rather frightening Faux Affably Evil personality and the fact she has the largest body count of any villain in the fic due to having gleefully erased the entire timeline and everyone in it several million times and she's most certainly this trope.
- Queen Chrysalis is this for the Reharmonized timeline. Where previous villains may have been more powerful, her planning, legions of Mooks, mind control powers (which see much more use than in canon), sadism, and knowledge of the Heart World make her quite possibly the greatest threat this timeline has ever faced.
- Chrysalis' Mad Scientist minion, Kabuto, is this for the Wedding Arc's side story focusing on Misfit Actual. Their story is actually has less action than the Mane Six's due to them acting covertly for the most part, and the fights they do have they tend to win fairly easily, with no real bad will towards their opponents, who are only trying to capture them. Then they go up against Kabuto, a Faux Affably Evil Mad Doctor who casually talks about performing monstrous experiments on his own kind and innocent ponies, and is also an incredibly dangerous opponent due to experimenting on himself. In addition to this, Kabuto is established as a mass murderer due to the number of people he's killed with his experiments, something his desire to vivisect Twilight and perform horrific experiments on the rest of the mane six makes abundantly clear is not exaggerated.
- The Chaos Verse (an official spinoff of the POV Series above) is pretty lighthearted until the Big Bad Nightmare Phobia shows up and nearly manipulates Fluttershy into killing herself.
- The Portal has Zobek, the leader of the Dark Ones. Upon first meeting Blizzard, Zobek absolutely curb stomps him and then stabs him with his tail, thus infecting the young dragon with his dark energy, causing him to nearly become a Dark One.
- The Powers of Harmony: While it was fairly obvious from the start that the story was ultimately going to go in a dark direction, it was pretty easy to ignore, given the story's mostly light tone for most of Act 1. Then, just after the Guards' Dark Secret and backstory are revealed at the beginning of Act 2, Cetus shows up, and everything goes straight to Hell.
- Queen of All Oni has Evil Sorcerer Lung, Daolon Wong's Bastard Understudy. He's only prominent in one chapter, but it's one of the darkest in the story, and his Cold-Blooded Torture of Jade is what starts her Sanity Slippage, which in turn is causing the story to start going down a dark path.
- A Rabbit Among Wolves: Elizabeth Tanner. She seems a like stern but reasonable manager for the SDC. In private, she is a remorseless serial rapist who exploits prejudice to force herself on Faunus men. Her violation of Jaune exposes him to the depths of corruption and exploitation found in Remnant. While the story does lighten back up once she leaves the narrative, it begins to explore more serious abuses people go through and never quite returns to the same light-hearted place that it began.
- The Racket-Rotter Chronicles has The Builder, a omnipotent, sociopathic entity who drags the story into much darker territory with their introduction. Before them, the story was simply a bunch of light-hearted vignettes.
- Remnant's Bizarre Adventure has Whitesnake. While Cinder's plans tend to fall short of success as a result of her overconfidence, Whitesnake is meticulous with his planning and understands how much of a threat the Joestars really are. Plus, he's the reason why Cinder was able to find many dangerous Stand Users, plus he arranged to have Cinder acquire the arrows in the first place. It's safe to say that Cinder wouldn't be nearly as dangerous without him.
- RE-TAKE: Initially came off as Peggy Sue fic where Shinji found the rest of the series after he escaped from Leliel was just a dream starts acting to prevent Asuka's fate in the actual series, leading to the two of them confessing their love... Then a second, badly injured and very embittered and angry Asuka appears that only Shinji can see, proving the first sign that everything is not going to work as perfectly at it first looks.
- The Rise of Darth Vulcan: The titular Darth Vulcan, aka Ted. Unlike most My Little Pony villains, he's a Evil Overlord who displays great competence, common sense, and makes the ponies realize just how weak they are against a truly serious villain. (Of course, it helps that the Alicorn Amulet grants him immense magical powers.)This guy isn't like you think. He's not clowny like Discord or loud and noisy like Nightmare Moon or wacky crazy like the Mane-iac or Ahuizotl. He's smart. and cold. and hard. He's always thinking, always making plans. And he's scarier than anything I've ever seen.
- The Road to be a Pokemon Master has a couple:
- Giovanni is the biggest one. While the fic has the same lighthearted tone as the anime, Giovanni here behaves like an actual, real life crime boss would, which naturally causes the tone to get considerably darker whenever he's present.
- His son Silver as well, being a rather brutal trainer who won't hesitate to order his Pokemon to use lethal force on Team Rocket grunts. Not to mention the amount of distress that he causes Ash whenever they meet due them being estranged half siblings.
- Shadows of Giants: Godzilla. Big time. While he's been confirmed by Word of God as an Anti-Hero, he's treated with the same degree of seriousness as he was in the 1954 film.
- Shards of Memory, the story takes a much more foreboding turn when Chaos makes his entrance. Killing Cosmos was just the start of the havoc his introduction caused.
- Silly Hat Productions appears at first to be just an Affectionate Parody of Umineko: When They Cry. Then Lambdadelta decides that Battler isn't taking the games seriously enough, and decides to throw in some motivation by revealing that since it's just a 'replica board', she can erase it. She then declares that for every episode where Battler fails to present a good theory, she'll erase one of the pieces who died in that game's scenario.
- Akatsuki as a whole in Son of the Sannin. Part I is a Cerebus Rollercoaster, alternating between lighthearted and serious arcs, but whenever an Akatsuki shows up, it spells that things are about to get very dark. By the Shippuden timeframe, they've taken a more active role in hunting the jinchuriki and their Tailed Beasts, and with it comes a significant decrease in humorous and lighthearted moments.
- Soul Eater: Troubled Souls
- Cancer Lucrenian's first appearance during the Introduction Arc finally give us something to look forward to in terms of conflict. It also gives a preview of her caliber as a villain. You certainly qualify when one of your first actions is trying to preemptively kill main characters.
- Medusa Gorgon singlehandedly plummets this story into Darker and Edgier territory by putting the main cast in mortal danger and making their limitations painfully obvious. She may be an Arc Villain, but she masterminds first entirely serious story arc, one that contains real dangers and serious developments.
- In Star Wars: Light in Dark Time, Jinn Skywalker fits this trope perfectly. His appearance marks the first legitimate villain threat, as well as the start of the Myth Arc. Admiral Zorg ups the ante when he begins to gain a role in the story, being calm and calculating, in contrast to Jinn's brash, Blood Knight tendencies.
- Star Wars: Paranormalities: While Maesterus is one of Zolph Vaelor's most dreaded foes throughout Episode I (Zolph is defeated by him three times, and he killed his father), he's a charismatic Anti-Villain at best, as he prefers not to kill his enemies. The Forceless Collective and their generals, the Archfiends, are not so kind in comparison. They are perfectly willing to kill and possess other beings without second thought (and for elaboration, the victims are consciously aware of it, and they don't get control of their bodies back unless they serve willingly). While they seem to have ambiguous morals in their debut appearances since they don't talk (usually) and are pretty bizarre to begin with, this gets jossed near the end of Episode I when they are revealed to be capable of sadism and are also willing to resort to psychological warfare.
- ChaosGallantmon from the Tamers Forever Series. Before his appearance, the series was a lighthearted romantic comedy series. However ChaosGallantmon's appearance kicks the series Myth Arc into high gear by triggering the series first Wham Episode. And his second appearance is the catalyst for the series Darkest Hour.
- To Hell and Back (Arrowverse).
- First, we have Zoom. While he made a cameo earlier in Arc III, his debutal in Arc IV is a turning point for worst in the story. The Speed Demon shows up during at chapter 81, kills most of the people at the Rathaway's Spring Gala, beats Barry up to a pulp live on TV then delivers a haunting warning to Central City saying that this is just the beginning. It only gets worse after this.
- The arrival of the Worldkillers (Purity, Pestillence and Reign) on Arc V causes the story to go trough a case of Cerebus Syndrome. They manage surpass even Zoom in terms strenght, power and cruelty. First, Pestillence causes the outbreak of a Kryptonian plague that kills hundreds of people, then Purity, who gained her plague powers, nearly kills Supergirl with it and then Reign shows up, beats Astra/Archangel to an inch of her life, again, in live TV.
- A Triangle in the Stars: There are ultimately two of these. Jasper and the Void. When either of these two show up, or are even mentioned, the story noticeably darkens. Gabriel tried, but he barely held a candle to them, and Bill himself started off as one, but ultimately passed the torch.
- Ahuizotl of all characters in The Two Sides of Daring Do seems to be this. The story is a large part focusing on Yearling dealing with an idealized clone of herself born from her books who proves to be Always Someone Better to her. Then Ahuizotl shows up in person, makes a comment that pushes Yearling's growing Cutie Mark Failure Insanity Syndrome over the edge, curbstomps Yearling when she tries to attack him in an Unstoppable Rage, and beats her unconscious. He solidifies this next chapter by revealing his plans are less about conquest and more about destruction For the Evulz, to the point he desires to reduce the entire world to a barren Death World if he could which her current plan would allow him to do. His reason for putting Daring in a Death Trap instead of killing her is also revealed to be pure unadulterated Sadism and a desire to make her final moments be slowly and painfully Dying Alone. He also beats the hell out of the clone due to her inexperience with him instead of his book counterpart, enjoying every minute of it. In the end, even though he's defeated, he gives the protagonists a serious beating that leaves them with broken bones in the Final Battle. Word of God has said he interprets the real Ahuizotl as an utter psychopath so it's no wonder he's this trope.
- Umi Tsuda in Windows of the Soul. The first time she shows up, she tries to kill Shizuru for killing her fiance, and the parts in which she's involved are some of the darker parts of the fic.
- Despite the fact that the villains from Zero 2: A Revision often always put the Digidestined on the ropes, there is always a feeling of hope that the Digidestined will eventually triumph over the dark forces. Darkheart aka Davis's corrupted form however, is an entirely different beast as his true entrance to the Digidestined involves him destroying the entire Primary Village as well as continously overpowering and tortures the entire Digidestined because he can, absorbing them one-by-one with the heroes unable to do anything other than run away from him to stop his continuous pursuit to become the greatest villain of all time. In short, his mere presence not only single-handedly prevents the Digidestined from returning to the real world and stop both Umbradevimon and Demon's invasion from leveling the entire city of Odaiba but also turns the story into one of the bleakest moment in the entire Zero 2 series.
