History KnightOfCerebus / Fanworks

** All that above pales in comparison to the dark, inescapable force of destruction that is [[BigBad Darth Nihilus]]. Whereas even Cinder had her humorous moments, ''nothing'' about Nihilus is ever PlayedForLaughs. He's an insidious EldritchAbomination bent on consuming all of existence and his [[TheCorrupter corruptive influence on Jaune]] is one-hundred percent PlayedForDrama. His inclusion in the story is almost single-handedly responsible for the fic being DarkerAndEdgier than either of its source material. It's no coincidence that the chapters featuring Nihilus' POV also happen to be some of the darkest chapters in the entire story. [[spoiler:Once he possesses Jaune's body and takes an active role in the plot, the story dives headfirst into the CerebusSyndrome and [[CharactersDroppingLikeFlies characters start dropping like flies]] as they are violently KilledOffForReal by [[HeroKiller Nihilus]].]]

** All that above pales in comparison to the kind of horror that [[BigBad Darth Nihilus]] brings to the table. Whereas even Cinder had her humorous moments, ''nothing'' about Nihilus is ever PlayedForLaughs. He's an insidious EldritchAbomination bent on consuming all of existence and his corruptive influence on Jaune is one-hundred percent PlayedForDrama. His involvement in the plot is almost single-handedly responsible for the story being DarkerAndEdgier than in canon and the plot immediately takes a darker turn whenever he appears. [[spoiler:After possessing Jaune's body, Nihilus introduces himself by [[CurbStompBattle curb-stomping]] the heroes and going on a rampage which culminates in the deaths of Qrow, Team ABRN, and dozens more innocent people.]]

** All that above pales in comparison to the kind of horror that [[BigBad Darth Nihilus]] brings to the table. Whereas even Cinder had her humorous moments, ''nothing'' about Nihilus is ever PlayedForLaughs. He's an insidious EldritchAbomination bent on consuming all of existence and his corruptive influence on Jaune is one-hundred percent PlayedForDrama. His involvement in the plot is almost single-handedly responsible for the story being DarkerAndEdgier than in canon and the plot immediately takes a darker turn whenever he appears. [[spoiler:After possessing Jaune's body, Nihilus introduces himself to the story by [[CurbStompBattle curb-stomping]] the heroes and going on a rampage which culminates in the deaths of Qrow, Team ABRN, and dozens more innocent people.]]

** All that above pales in comparison to the kind of horror that [[BigBad Darth Nihilus]] brings to the table. Whereas even Cinder had her humorous moments, ''nothing'' about Nihilus is ever PlayedForLaughs. He's an insidious EldritchAbomination bent on consuming all of existence and his corruptive influence on Jaune is one-hundred percent PlayedForDrama. His involvement in the plot is almost single-handedly responsible for the story being DarkerAndEdgier than in canon and the plot immediately takes a darker turn whenever he appears. [[spoiler:After possessing Jaune, Nihilus makes his official debut by curb-stomping the heroes, killing dozens of civilians en masse, and causing the deaths of several major characters as well as a dozen minor characters.]]

** All that above pales in comparison to the kind of horror that [[BigBad Darth Nihilus]] brings to the table. Whereas even Cinder had her humorous moments, ''nothing'' about Nihilus is ever PlayedForLaughs. He's an insidious EldritchAbomination bent on consuming all of existence and his corruptive influence on Jaune is one-hundred percent PlayedForDrama. His involvement in the plot is almost single-handedly responsible for the story being DarkerAndEdgier than in canon and the plot immediately takes a darker turn whenever he appears. [[spoiler:After possessing Jaune, Nihilus makes his official debut by curb-stomping the heroes, killing civilians en masse, and causing the deaths of several major characters as well as a dozen minor characters.]]

** All that above pales in comparison to the level of horror that [[BigBad Darth Nihilus]] brings to the table. Whereas even Cinder had her humorous moments, ''nothing'' about Nihilus is ever PlayedForLaughs. He's an insidious EldritchAbomination bent on consuming all of existence and his corruptive influence on Jaune is one-hundred percent PlayedForDrama. His involvement in the plot is almost single-handedly responsible for the story being DarkerAndEdgier than in canon and the plot immediately takes a darker turn whenever he appears. [[spoiler:After possessing Jaune, Nihilus makes his official debut by curb-stomping the heroes, killing civilians en masse, and causing the deaths of several major characters as well as a dozen minor characters.]]

* ''Fanfic/JauneArcLordOfHunger'': While not without drama, the story is fairly lighthearted at first, focusing on Jaune learning to control his new powers while bonding with his teammates. That all changes once the terentatek comes along. It's a nigh-unstoppable monster mutated by the Dark Side and far more dangerous than any [[TheUsualAdversaries Grimm]]. It's the first serious threat that the protagonists face and comes the closest out of any villain to actually ''killing'' Jaune. The scene where the creature attacks includes the first instance of {{Gorn}} in a story that had previously been tame with its violence. If it wasn't for a [[DeusExMachina last-minute]] GunshipRescue, the entire main cast would be dead. In addition, the terentatek's debut marks the start of Jaune's ProtagonistJourneyToVillain as he starts drawing power from the Dark Side and becomes more [[TookALevelInJerkass temperamental and abrasive]] in the chapters that follow.

* ''Fanfic/JauneArcLordOfHunger'': While not without drama, the story is fairly lighthearted at first, focusing on Jaune learning to control his new powers while bonding with his teammates. That all changes once the terentatek comes along. For the heroes, the terentatek is the first truly serious threat they've faced. It's a powerful Dark Side creature more dangerous than any [[TheUsualAdversaries Grimm]] they've fought and it comes the closest out of any antagonist to actually ''killing'' Jaune while shrugging off the heroes' strongest attacks. The scene where the terentatek attacks Jaune also includes the first instance of {{Gorn}} in a story that had previously been family-friendly with its violence. If it wasn't for a [[DeusExMachina last-minute]] GunshipRescue, the entire main cast would be dead. In addition, the terentatek's debut marks the start of Jaune's ProtagonistJourneyToVillain as he starts drawing power from the Dark Side and becomes more [[TookALevelInJerkass temperamental and abrasive]] in the chapters that follow.

* ''Fanfic/JauneArcLordOfHunger'': While not without drama, the story is fairly lighthearted at first, focusing on Jaune learning to control his new powers while bonding with his teammates. That all changes once the terentatek comes along. For the heroes, the terentatek is the first truly serious threat they've faced. It's an powerful Dark Side creature more dangerous than any [[TheUsualAdversaries Grimm]] they've fought and it comes the closest out of any antagonist to actually ''killing'' Jaune while shrugging off the heroes' strongest attacks. The scene where the terentatek attacks Jaune also includes the first instance of {{Gorn}} in a story that had previously been family-friendly with its violence. If it wasn't for a [[DeusExMachina last-minute]] GunshipRescue, the entire main cast would be dead. In addition, the terentatek's debut marks the start of Jaune's ProtagonistJourneyToVillain as he starts drawing power from the Dark Side and becomes more [[TookALevelInJerkass temperamental and abrasive]] in the chapters that follow.

* ''Fanfic/JauneArcLordOfHunger'':
** While not without drama, the story is fairly lighthearted at first, focusing on Jaune learning to control his new powers while bonding with his teammates. That all changes once the terentatek comes along. For the heroes, the terentatek is the first truly serious threat they've faced. It's an powerful Dark Side creature more dangerous than any [[TheUsualAdversaries Grimm]] they've fought and it comes the closest out of any antagonist to actually ''killing'' Jaune while shrugging off the heroes' strongest attacks. The scene where the terentatek attacks Jaune also includes the first instance of {{Gorn}} in a story that had previously been family-friendly with its violence. If it wasn't for a [[DeusExMachina last-minute]] GunshipRescue, the entire main cast would be dead. In addition, the terentatek's debut marks the start of Jaune's ProtagonistJourneyToVillain as he starts drawing power from the Dark Side and becomes more [[TookALevelInJerkass temperamental and abrasive]] in the chapters that follow.

* ''Fanfic/JauneArcLordOfHunger'': While not without drama, the story is fairly lighthearted at first, focusing on Jaune learning to control his new powers while bonding with his teammates. That all changes once the terentatek comes along. For the heroes, the terentatek is the first truly serious threat they've faced. It's an immensely powerful Dark Side creature more dangerous than any [[TheUsualAdversaries Grimm]] they've fought and it nearly kills Jaune while shrugging off the heroes' strongest attacks. The scene where the terentatek attacks Jaune also includes the first instance of {{Gorn}} in a story that had previously been family-friendly with its violence. If it wasn't for a [[DeusExMachina last-minute]] GunshipRescue, the entire main cast would be dead. The terentatek's appearance also marks the start of Jaune's ProtagonistJourneyToVillain as he starts drawing power from the Dark Side and becomes more [[TookALevelInJerkass temperamental and abrasive]] in the chapters that follow.

* ''Fanfic/JauneArcLordOfHunger'': While not without drama, the story is fairly lighthearted at first, focusing on Jaune learning to control his new powers while bonding with his teammates. That all changes once the terentatek comes along. For the heroes, the terentatek is the first truly serious threat they've faced. It's an immensely powerful Dark Side creature more dangerous than any Grimm they've fought and it nearly kills Jaune while shrugging off the heroes' strongest attacks. The scene where the terentatek attacks Jaune also includes the first instance of {{Gorn}} in a story that had previously been family-friendly with its violence. If it wasn't for the intervention of [[BadassTeacher Professor Goodwitch]], the entire main cast would be dead. The terentatek's appearance also marks the start of Jaune's ProtagonistJourneyToVillain as he starts drawing power from the Dark Side and becomes more [[TookALevelInJerkass temperamental and abrasive]] in the chapters that follow.

* ''Fanfic/HauntedMansionAndTheHatboxGhost'': 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.

* ''Fanfic/JauneArcLordOfHunger'': While not without drama, the story is fairly lighthearted at first, focusing on Jaune learning to control his new powers while bonding with his teammates. That all changes once the terentatek comes along. For the heroes, the terentatek is the first truly serious threat they've faced. It's an immensely powerful Dark Side creature more dangerous than any Grimm they've fought and it nearly kills Jaune while shrugging off the heroes' strongest attacks. If it wasn't for [[BadassTeacher Professor Goodwitch]], the entire main cast would be dead. The chapter where the terentatek debuts also represents the beginning of Jaune's ProtagonistJourneyToVillain as he starts drawing power from the Dark Side and becomes more [[TookALevelInJerkass temperamental and abrasive]] in the chapters that follow.

* ''Fanfic/JauneArcLordOfHunger'': While not without drama, the story is fairly lighthearted at first, focusing on Jaune learning to control his new powers while bonding with his teammates. That all changes once the terentatek comes along. For the heroes, the terentatek is the first truly serious threat they've faced. It's an immensely powerful Dark Side creature more dangerous than any Grimm they've fought and it nearly kills Jaune while shrugging off the heroes' strongest attacks. If it wasn't for [[BadassTeacher Professor Goodwitch]], the entire main cast would be dead. The chapter where the terentatek debuts also represents the beginning of Jaune's ProtagonistJourneyToVillain as he starts drawing more power from the Dark Side and becomes more [[TookALevelInJerkass temperamental and abrasive]] in the chapters that follow.

* ''Fanfic/JauneArcLordOfHunger'': The terentatek from "Fear". Up until that point, the story had been mostly lighthearted and the closest thing to an antagonist was the school bully Cardin, who Jaune had already dealt with in a previous chapter. Then comes along the terentatek, which quickly takes things to a ''whole'' new level, [[MoodWhiplash turning a heartwarming moment between friends into a desperate struggle for survival]]. For the heroes, the terentatek represents the first time that any of them have ever faced a serious opponent which outclasses them in almost every way. It no-sells the heroes' best attacks, [[TheWorfEffect curb-stomps Pyrrha and Yang]], and nearly kill Jaune by [[GuttedLikeAFish tearing through his stomach]]. The entire fight has a very tense atmosphere as Ren desperately tries to prevent Jaune from bleeding out while the others are barely holding their own against the monster. The chapter where the terentatek debuts also represents the starting point of [[ProtagonistJourneyToVillain Jaune's slow descent into the Dark Side]] as he starts to [[TookALevelInJerkass become more abrasive]] in the following chapters.

* ''Fanfic/ATriangleInTheStars'': There are ultimately two of these. [[spoiler: Jasper and the Void.]] When either of these two show up, or are even mentioned, the story noticeably darkens. [[spoiler: Gabriel tried, but he barely held a candle to them, and Bill himself started off as one, but ultimately [[HeelFaceTurn passed the torch]].]]
* ''Fanfic/ChildOfTheStorm'':
** 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.
%%** Sinister's involvement arguably makes it even darker.

* ''Fanfic/DungeonKeeperAmi'': 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 [[spoiler: 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 ZanyScheme -ness, his [[SlasherSmile sadistic streak]] and ability to [[LaughingMad bounce back]] from crushing defeat is intimidating to the extreme.
* [[spoiler: [=ChaosGallantmon=]]] from the ''Fanfic/TamersForeverSeries''. Before his appearance, the series was a lighthearted romantic comedy series. However [[spoiler: [=ChaosGallantmon=]]]'s appearance kicks the series MythArc into high gear by triggering the series first WhamEpisode. And his second appearance is the catalyst for the series DarkestHour.
%%** For an even more [[HeroKiller extreme]] version of this, we have [[spoiler:Daemon]]. See DarkestHour for more information.
* Saint Ayame and Saint Sarutobi from ''Fanfic/OnePieceParallelWorks''. We first see them trying to enslave an entire island, [[spoiler: 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 ([[spoiler: even though her parents faked their deaths]]) don't even begin to describe how they've also [[spoiler: almost brainwashed Holden by sending him to a boarding school for the children of the Tenryuubito]]. It's also implied that [[spoiler: Saint Ayame frequently beat Yuki-Rin for her love of pirates]].
* ''Fanfic/GettingBackOnYourHooves'' had some sad moments in the beginning, but mostly a rather lighthearted story about Trixie trying to do exactly what the title says...Then [[BigBad Checker]] [[CorruptCorporateExecutive Monarch]] enters the picture. WordOfGod states her mannerisms were based off those of a [[TheSociopath sociopath]] if that's any indication. Example? [[spoiler:She MindRaped 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.
* [[spoiler: Gilda]]'s initial appearance in ''[[{{Fanfic/AceCombatEquestriaChronicles}} Ace Combat: The Equestrian War]]'' ends with her breaking Medley's wings and causing a HeroicBSOD 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.

* ''Fanfic/PonyPOVSeries''
** [[spoiler: [[EnemyWithin 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 [[spoiler: Loneliness]] brought with her. Not only that, but only a couple of chapters later the Princess [[spoiler: Gaia]] arc started up.
** Shining Armor's arc has [[BigBad General-Admiral Makarov]]. Things take a turn for the serious when he shows up, whereas before it was all pretty lighthearted [[spoiler: minus an early appearance by [[EldritchAbomination the Stalker]]]]. And then even more so once we find out [[spoiler: he's an [[HumanoidAbomination Equineoid Abomination]] who [[OnlyICanKillHim only Shining may be able to defeat]]]].
** [[spoiler: Nightmare Eclipse/Paradox manages to be this for ''[[BadFuture Dark World]]'', which was ''already'' DarkerAndEdgier. When the story finally turns to her, it instantly becomes a [[WhamEpisode Wham]] ''[[WhamEpisode 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 GroundhogDayLoop plan. Add in her rather frightening FauxAffablyEvil 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 [[LongGame planning]], legions of {{Mooks}}, mind control powers (which see much more use than in canon), [[{{Sadist}} sadism]], and [[spoiler: knowledge of the Heart World]] make her quite possibly the greatest threat this timeline has ever faced.
** Chrysalis' MadScientist minion, Kabuto, is this for the Wedding Arc's [[HeroOfAnotherStory 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 FauxAffablyEvil MadDoctor who casually talks about performing monstrous experiments on his own kind and innocent ponies, [[spoiler: 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.

* In ''Fanfic/MyLittleDenarians'', the Denarians. Discord may be more powerful, but the Denarians are more ''evil''.
* Fanfic/ShardsOfMemory, the story takes a much more foreboding turn when Chaos makes his entrance. [[spoiler:Killing Cosmos]] was just the start of the havoc his introduction caused.
* The [[Fanfic/PonyPOVSeriesChaosVerse Chaos Verse]] (an official spinoff of the ''POV Series'' above) is pretty lighthearted until the BigBad [[spoiler: [[EnemyWithout Nightmare Phobia]]]] shows up and nearly manipulates [[spoiler: Fluttershy]] into [[DrivenToSuicide killing herself]].
* Umi Tsuda in [[http://www.fanfiction.net/s/4004316/1/Windows-of-the-Soul Windows of the Soul]]. The first time she shows up, she [[spoiler: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.

** Subverted with [[spoiler: Chrysalis]]. At first it looked like she was going to be a Knight, but instead was [[VillainDecay reduced to]] an IneffectualSympatheticVillain, whose one major act of villainy [[spoiler: (framing Rarity being a changeling)]] was negated within hours.
* ''Fanfic/ThePowersOfHarmony'': 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' DarkSecret and backstory are revealed at the beginning of Act 2, [[BigBad Cetus]] shows up, and everything goes straight to Hell.
* ''[[FanFic/StarWarsParanormalitiesTrilogy 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 [[YouKilledMyFather he killed his father]]), he's a charismatic AntiVillain at best, as he prefers not to kill his enemies. The [[TheLegionsOfHell Forceless Collective]] and their generals, the [[SealedEvilInACan Archfiends]], are not so kind in comparison. They are perfectly willing to kill and [[DemonicPossession possess]] other beings without second thought (and for elaboration, [[AndIMustScream 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 [[EldritchAbomination pretty bizarre to begin with]], [[spoiler: 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 [[DespairEventHorizon psychological warfare.]]]]
* ''Fanfic/ShadowsOfGiants'': Godzilla. [[TheDreaded Big]] [[AssKickingEqualsAuthority time]]. While he's been confirmed by WordOfGod as an AntiHero, he's treated with the same degree of seriousness as he was in the 1954 film.
* In ''Fanfic/PerfectionIsOverrated''
** Hitomi Kirihara is the first [[ParodySue SUE]] with hostile intentions toward the [[Anime/MyHime Himes]], and abuses her MindControl 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.
** [[spoiler:Bachiko and Meiko]] present more of a threat to the Himes than most of the [=SUEs=], [[spoiler:setting them against each other and playing into the canon antagonists' plans]]. By the end of Chapter 19, [[spoiler: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]].
* There's an amusing attempt to ''invoke'' this in FanFic/ANewOrder. 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. WordOfGod 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.
* [[spoiler: Professor Moriarty]] in the first finale of ''Fanfic/ChildrenOfTime''. There have been a lot of monstrous beings and despicable actions to date, but ''no one'' with as thorough a vendetta against Literature/SherlockHolmes as [[spoiler:the Professor]]. Notably, within 5,000 words of his introduction, the whole world basically goes to hell.
* Denkuma in Volume I of [[http://www.fanfiction.net/s/5973337/1/Dragon-Ball-X-Volume-I-Eternal-Protectors 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. [[spoiler: 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.
* Happens ''twice'' in ''Fanfic/CalvinAndHobbesTheSeries'' to indicate that CerebusSyndrome is kicking in harder:
** 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 TakeOverTheWorld [[spoiler:and destroy [[DoAnythingRobot the MTM]]]]. It takes a ''lot'' to defeat them.
** The season 5 (and series) finale "Black Rain" abruptly introduces ''Franchise/{{the Slender Man|Mythos}}'' of all people, and his appearance is a haunting as always - ''especially'' when [[spoiler:he [[NeverFoundTheBody "kills"]] Thunderstorm and Shadow at the end]].
* ''Manga/ReTake'': Initially came off as PeggySue 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.
* ''FanFic/QueenOfAllOni'' has EvilSorcerer [[SmugSnake Lung]], Daolon Wong's BastardUnderstudy. He's only prominent in one chapter, but it's one of the darkest in the story, and his ColdBloodedTorture of [[VillainProtagonist Jade]] is what starts her SanitySlippage, which in turn is causing the story to start going down a dark path.
* As soon as [[spoiler: [[SerialKiller Beyond Birthday]]]] shows up in ''FanFic/ConstantTemptation'' things get really dark, really fast. [[UpToEleven He's somehow made even scarier than he is in canon.]]
* ''FanFic/PokemonMysteryDungeonHopeandFaithSaga'' starts getting ugly once Unod the World Destroyer appears.
%%* ''Film/TheRugratsMovie: The Shadow of Scar Snout'': Scar Snout the Wolf is already pretty intimidating in the actual movie and this story shows him to be even worse. Taking the idea that the world exists in the same universe as ''Series/TheWildThornberrys'', it tackles the sentience of Scar Snout with not only his willingness and sadistic glee in targeting innocent human babies, but targeting humans in general and deciding to wipe out his own pack to not have to live by their standards anymore.
* ''Fanfic/SillyHatProductions'' appears at first to be just an AffectionateParody of ''VisualNovel/UminekoWhenTheyCry''. 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 [[DeaderThanDead erase one of the pieces who died in that game's scenario]].
* The Vocaloid fanfiction [[https://www.fanfiction.net/s/5789061/1/Hear-my-Song Hear my Song!]] has IA. She's first introduced as an Korean IdolSinger who Miku listens to on the radio, and then as Yukari's StalkerWithACrush. And ''then'' she breaks [=SeeU=].
* In ''Fanfic/StarWarsLightInDarkTime'', Jinn Skywalker fits this trope perfectly. His appearance marks the first legitimate villain threat, as well as the start of the MythArc. 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, BloodKnight tendencies.
* Fanfic/EquestriasFirstHuman 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 [[spoiler: mutilate one of his subordinates for failing a petty order.]]

* In ''Fanfic/TheParselmouthOfGryffindor'', Barty Crouch Jr. plays this role. Pre-Crouch plot: no villain, Voldemort is a silver monkey, fun and good times. Post-Crouch plot: [[OurZombiesAreDifferent Inferi]] and [[spoiler: [[YourDaysAreDying 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 [[GiantSpider Acromantula]] [[TheHorde Army]]'s attack is portrayed much more seriously than most other events in the story as well, and is the only time [[spoiler:someone dies in the story so far, although only nameless RedShirts.]]
* ''Ahuizotl'' [[BewareTheSillyOnes of all characters]] in ''Fanfic/TheTwoSidesOfDaringDo'' 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 AlwaysSomeoneBetter to her. Then Ahuizotl shows up in person, makes a comment that pushes Yearling's growing Cutie Mark Failure Insanity Syndrome over the edge, [[spoiler:[[CurbstompBattle curbstomps Yearling]] when she tries to attack him in an UnstoppableRage, and [[NoHoldsBarredBeatdown beats her unconscious]]]]. He solidifies this next chapter by revealing his plans are less about conquest and more [[OmnicidalManiac about destruction]] ForTheEvulz, to the point he desires to reduce the entire world to a barren DeathWorld if he could [[spoiler:which her current plan would allow him to do]]. His reason for putting Daring in a DeathTrap instead of killing her is also revealed to be pure unadulterated {{Sadis|t}}m and a desire to make her final moments be slowly and painfully DyingAlone. He also [[spoiler: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 FinalBattle. WordOfGod has said [[AlternateCharacterInterpretation he interprets the real Ahuizotl as an utter psychopath]] so it's no wonder he's this trope.

* Despite the fact that the villains from ''FanFic/Zero2ARevision'' 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. [[SuperPoweredEvilSide 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 [[ForTheEvulz 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 [[DarkestHour bleakest moment in the entire Zero 2 series]].
* ''Fanfic/TheRiseOfDarthVulcan'': The titular Darth Vulcan, aka Ted. Unlike most ''My Little Pony'' villains, he's a EvilOverlord 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.''
* ''[[FanFic/IAgainstIMeAgainstYou I Against I, Me Against You]]'': ''Wyoming'' [[BewareTheSillyOnes 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.

* ''Fanfic/TheDarkSideOfTheMirrorVerse'':
** [[spoiler:[[TheDreaded Mirror!Spitfire]]]]. While there are some serious moments, ''anything'' dealing with her is treated seriously, and Rainbow Crash is absolutely ''terrified of her''. [[spoiler:For good reason, as her abuse left her the broken wreck she is now]], and she's also [[spoiler:responsible for Fluttershy's BystanderSyndrome.]] Not to mention that [[spoiler:she's TheQuisling and willingly sided with Mirror Celestia to help destroy Cloudsdale.]]
** [[spoiler:Twilight's SuperpoweredEvilSide, 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. [[spoiler:She puts Trixie in a DeadlyGame, nearly freezes her solid, almost kills her and Maud, and comes very close to destroying Canterlot.]]
* ''Fanfic/SoulEaterTroubledSouls''
** 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 DarkerAndEdgier territory by putting the main cast in mortal danger and making their limitations painfully obvious. She may be an ArcVillain, but she masterminds first entirely serious story arc, one that contains real dangers and serious developments.
* ''[[http://www.fimfiction.net/story/237978/how-trixie-somehow-saved-hearths-warming How Trixie (Somehow) Saved Hearth's Warming]]'' has the BigBad Leidr. While the secondary villain the Rat King isn't a push over and quite dangerous, he's still a LargeHam 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 CurbstompBattle in his favor. [[spoiler:He's also a very powerful sapient Windigo and carries all their frightening attributes.]] According to WordOfGod, this was based off of how some Christmas Specials (which the story is a {{Homage}} to) had surprisingly frightening villains.
* ''Fanfic/TheRacketRotterChronicles'' 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.

* The ''[[Fanfic/{{Cinderjuice}} Contractually Obligated Chaos]]'' series has thus far introduced two. The first is Erebos, ArcVillain of the second story; he's a LivingShadow whose main scheme for weakening his victims is to BreakThemByTalking until they make a DealWithTheDevil. Even worse is Vasile, in the third story, a specific type of murderous poltergeist who ''feeds on children''.
* ''Fanfic/CommonSense'' makes the TropeNamer TerribleTrio of ''Team Rocket'' into one of these, with a severe increase in competency and a large amount of collateral damage (mostly by invoking TheBadGuyWins 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 ChronicHeroSyndrome into a full-blown martyr complex (because as he sees it he's TheOnlyOne 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 WorthyOpponent card on Ash... mostly as a way to DrawAggro so he can't help people.
* Chapter 22 of ''Fanfic/PokemonResetBloodlines'' introduces [[PoisonousPerson Belladonna]] [[DarkActionGirl Tyrian]], who by [[WhamEpisode 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 [[DiabolicalMastermind Bloodline King]] or [[EldritchAbomination MissingNo]], she still becomes the first villain in the main story to kill someone on screen as part of a ploy to [[spoiler: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 [[OOCIsSeriousBusiness uncharacteristically silent]]. She also turns Pokemon's, both the original series and the fics, [[spoiler: IdenticalStranger trope on its head]], suggesting that it is in fact another trope entirely: [[spoiler: LongLostRelative]]. Notably, it's only after she appears that the fic finally reveals the Reset verse's [[TheSocialDarwinist version]] of Sabrina, and in the side stories [[NoNonsenseNemesis Capriccio]].
* In [[Anime/NeonGenesisEvangelion canon]] and ''Fanfic/NeonMetathesisEvangelion'' alike, Bardiel fulfils that role. [[spoiler:Whereas most angel battles before are relatively easy, Bardiel requires Rei to sacrifice herself. And afterwards, the tone is somewhat darker.]]
* ''Fanfic/HauntedMansionAndTheHatboxGhost'': 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.
* ''Fanfic/OldWest'' 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 [[DomesticAbuse domestic violence]] is one of the darkest moments of the story. Though Grace's lover Rattlesnake Jake gives Benjamin his comeuppance ([[spoiler:a painful death through a venomous bite]]), Grace's [[HeroicBSOD 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 [[BigBad Dufayel]] to legally claim the ownership of Grace's property. Benjamin's failure is [[RageBreakingPoint the last]] [[VillainousBreakdown straw]] for Dufayel who finally decides to [[ThisMeansWar stop playing by the law and use more drastic measures against the heroes]].

* ''Fanfic/CitadelOfTheHeart'' 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 KnightOfCerebus from ''Truth and Ideals'' as detailed below:
** ''Truth and Ideals'': Regulus is a nicknamed Lucario having originally been owned by Ash's DisappearedDad when he was just a Riolu, and when we first actually get to see him, he [[WhamLine casually reveals]] more information about Ash's past [[WhamShot as well as]] showing possession of a [[SuperMode Lucarionite Mega Stone]], and his debut ends up [[WhamEpisode leaving Ash comatose for a few days on end]] because of Regulus [[DoesNotKnowHisOwnStrength not knowing his own strength]].
** ''Sword Art Online: Special Edition'': [[TheJuggernaut Grandis]], the primary AuthorAvatar of the entire continuity, [[WhamShot is introduced in a fashion that]] [[MysteriousPast answers many questions as to where Chronicler came from and why he has his distinct powers,]] [[EstablishingCharacterMoment but most importantly]] [[WhamEpisode opens up a whole new can of worms]] [[WhamLine in the fact Chronicler is only half of what Grandis himself is 100% of.]] What little we see of Grandis [[OlympusMons showcases him to not only be a far stronger opponent than Chronicler could ever be]], but also the fact [[TranquilFury Grandis is restraining]] ''[[TranquilFury all]]'' [[TranquilFury of his abilities and frustrations]] [[AwakeningTheSleepingGiant 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.]]
* ''Fanfic/FreakinGensokyo'': Matt, the main character's friend, sees Gensokyo as little more than a playground for murdering people [[ImprovisedWeapon with scissors]]. It is played either [[PlayedForLaughs for laughs]] or neutrally to begin with, right up until the reveal that Matt [[spoiler:murdered Maria's mother]].
* ''Fanfic/JauneArcLordOfHunger'': The terentatek from "Fear". Up until that point, the story had been mostly lighthearted and the closest thing to an antagonist was the school bully Cardin, who Jaune had already dealt with in a previous chapter. Then comes along the terentatek, which quickly takes things to a ''whole'' new level, [[MoodWhiplash turning a heartwarming moment between friends into a desperate struggle for survival]]. For the heroes, the terentatek represents the first time that any of them have ever faced a serious opponent which outclasses them in almost every way. It no-sells the heroes' best attacks, [[TheWorfEffect curb-stomps Pyrrha and Yang]], and nearly kill Jaune by [[GuttedLikeAFish tearing through his stomach]]. The entire fight has a very tense atmosphere as Ren desperately tries to prevent Jaune from bleeding out while the others are barely holding their own against the monster. The chapter where the terentatek debuts also represents the starting point of [[ProtagonistJourneyToVillain Jaune's slow descent into the Dark Side]] as he starts to [[TookALevelInJerkass become more abrasive]] in the following chapters.

* The Geeky Zoologist's [[Fanfic/JurassicWorld2020 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 [[spoiler: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 [[spoiler: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.]]
* The ''[[http://askprincessmolestia.tumblr.com/ Ask Princess Molestia]]'' blog is typically about the wacky and lighthearted hijinks of a MemeticMolester and an endearingly dorky GamerChick. However, whenever Fausticorn swings by for a visit, it careens into a rather dark and depressing drama that shows Molestia has some ''[[FreudianExcuse serious]]'' [[MommyIssues 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.
* ''WebVideo/MyLittlePonyTheMentallyAdvancedSeries'':
** The Monster from Rainbow Dash Presents: The Haunting. While The AbridgedSeries has always been chalk full dark and even depressing elements, as you would be expected in a CrapsaccharineWorld version of Equestria, ruled by an insane EvilGod, with a secret war being fought by {{Eldritch Abomination}}s and a cynical atmosphere, they had always been PlayedForLaughs. Until this guy showed up and {{Mind Rape}}d Twilight into helping it try to devour a couple of the characters, while singing its surprisingly menacing VillainSong "Bones and Skin".
** Likewise, when [[spoiler: Twilight starts hallucinating Yellow Star]] in RDP: The Star In Yellow, the story starts shifting from ComedicSociopathy to CosmicHorrorStory.
* Akatsuki as a whole in ''Fanfic/SonOfTheSannin''. Part I is a CerebusRollercoaster, 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.

* ''Fanfic/ARabbitAmongWolves'': Elizabeth Tanner. She seems a like stern but reasonable manager for the [=SDC=]. [[spoiler: 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.
* ''Fanfic/CindersAndAshesTheChroniclesOfKamenRiderDante'' has Magane as one. While she is one in [[Anime/ReCreators 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 [[spoiler:his brief FaceHeelTurn]]. While an honorable mention goes to Vega for bringing the [[MonsterOfTheWeek Kaizo-Majin]] into the world and Malacoda [[spoiler: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.
* ''Fanfic/ChildrenOfRemnant'':
** 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 [[spoiler:Marcus Black]] enters the narrative, it gets a lot more serious in a manner that never disappears, as [[spoiler:Marcus is the assassin the conspiracy hires to kill Jaune]].
* ''Fanfic/OneStepBackwardsAndThreeForwards'' has G, aka [[spoiler: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 [[spoiler:Alya takes him up on his offer]], with the bodies starting to pile up.
* ''Fanfic/EquestriaGirlsAFairlyOddFriendship'': The story, while somewhat more dramatic, is a mostly lighthearted fare. Then [[spoiler: the Dazzlings]] move into the picture, and while they do have humorous moments, their villainous actions are not PlayedForLaughs. [[spoiler: 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 NoHoldsBarredBeatdown, and threaten to throw Trixie off the roof if he doesn't grant their wish to rule Dimmsdale.]]

* Fanfic/FreakinGensokyo: Matt, the main character's friend, sees Gensokyo as little more than a playground for murdering people [[ImprovisedWeapon with scissors]]. It is played either [[PlayedForLaughs for laughs]] or neutrally to begin with, right up until the reveal that Matt [[spoiler:murdered Maria's mother]].

* ''FanFic/CindersAndAshesTheChroniclesOfKamenRiderDante'' has Magane as one. While she is one in [[Anime/ReCreators 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 [[spoiler:his brief FaceHeelTurn]]. While an honorable mention goes to Vega for bringing the [[MonsterOfTheWeek Kaizo-Majin]] into the world and Malacoda [[spoiler: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.

* ''FanFic/DungeonKeeperAmi'': 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 [[spoiler: 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 ZanyScheme -ness, his [[SlasherSmile sadistic streak]] and ability to [[LaughingMad bounce back]] from crushing defeat is intimidating to the extreme.
* [[spoiler: [=ChaosGallantmon=]]] from the ''FanFic/TamersForeverSeries''. Before his appearance, the series was a lighthearted romantic comedy series. However [[spoiler: [=ChaosGallantmon=]]]'s appearance kicks the series MythArc into high gear by triggering the series first WhamEpisode. And his second appearance is the catalyst for the series DarkestHour.

* ''FanFic/SillyHatProductions'' appears at first to be just an AffectionateParody of ''VisualNovel/UminekoWhenTheyCry''. 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 [[DeaderThanDead erase one of the pieces who died in that game's scenario]].

* ''FanFic/TheEquestrianWindMage'' has [[TheDragon Dethl]], oh so much. While Season 1 is primarily SliceOfLife, his presence immediately makes things deathly serious -- he [[DemonicPossession possesses Diamond Tiara]] and uses her to try and kill the Cutie Mark Crusaders, in order to hurt Vaati (who had [[HappilyAdopted adopted]] Scootaloo), for no reason than anger at Vaati's HeelFaceTurn. 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 ''[[HiddenVillain before we even know who he is]]''. And the reveal of his identity, and his connection to the [[ReligionOfEvil Church of Majora]], in the season finale just opens the path for the CerebusSyndrome that the next two seasons suffer from.

* ''FanFic/GettingBackOnYourHooves'' had some sad moments in the beginning, but mostly a rather lighthearted story about Trixie trying to do exactly what the title says...Then [[BigBad Checker]] [[CorruptCorporateExecutive Monarch]] enters the picture. WordOfGod states her mannerisms were based off those of a [[TheSociopath sociopath]] if that's any indication. Example? [[spoiler:She MindRaped 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.

* T''FanFic/PonyPOVSeries''

* In ''FanFic/TheDresdenFillies'', the story takes a darker turn when [[spoiler:Trixie and the Nightmare kidnap Spike.]]
* In ''FanFic/MyLittleDenarians'', the Denarians. Discord may be more powerful, but the Denarians are more ''evil''.

* ''FanFic/EarthAndSky'': 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.

* ''FanFic/ThePowersOfHarmony'': 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' DarkSecret and backstory are revealed at the beginning of Act 2, [[BigBad Cetus]] shows up, and everything goes straight to Hell.

*** Sinister's involvement arguably makes it even darker.

** For an even more [[HeroKiller extreme]] version of this, we have [[spoiler:Daemon]]. See DarkestHour for more information.

* The ''FanFic/PonyPOVSeries'' has [[spoiler: [[EnemyWithin 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 [[spoiler: Loneliness]] brought with her. Not only that, but only a couple of chapters later the Princess [[spoiler: Gaia]] arc started up.

** Hitomi Kirihara is the first [[ParodySue SUE]] with hostile intentions toward the [[Anime/MaiHime Himes]], and abuses her MindControl 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.

** For an even more [[HeroKiller extreme]] version of this, we have [[spoiler: Daemon]]. See DarkestHour for more information.
* Saint Ayame and Saint Sarutobi from Fanfic/OnePieceParallelWorks. We first see them trying to enslave an entire island, [[spoiler: 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 ([[spoiler: even though her parents faked their deaths]]) don't even begin to describe how they've also [[spoiler: almost brainwashed Holden by sending him to a boarding school for the children of the Tenryuubito]]. It's also implied that [[spoiler: Saint Ayame frequently beat Yuki-Rin for her love of pirates]].

* ''FanFic/CindersAndAshesTheChroniclesOfKamenRiderDante'' has Magane as one. While she is one in [[Anime/ReCreators 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 and her first full appearance brings with it [[spoiler:Hoshi's brief FaceHeelTurn]]. While an honorable mention goes to Vega for bringing the [[MonsterOfTheWeek Kaizo-Majin]] into the world and Malacoda [[spoiler: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.

* The ''[[http://askprincessmolestia.tumblr.com/ Ask Princess Molestia]]'' blog is typically about the wacky and lighthearted hijinks of a MemeticMolester and an {{Adorkable}} GamerChick. However, whenever Fausticorn swings by for a visit, it careens into a rather dark and depressing drama that shows Molestia has some ''[[FreudianExcuse serious]]'' [[MommyIssues 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.

* ''FanFic/DungeonKeeperAmi'': a strange, strange example in the form of [[CrazyAwesome Mukrezar]]. Mukrezar is a goofy, slightly manic Keeper of dubious competence. He doesn't even look threatening, he's a pink-haired elf! Following [[spoiler: 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 ZanyScheme -ness, his [[SlasherSmile sadistic streak]] and ability to [[LaughingMad bounce back]] from crushing defeat is intimidating to the extreme.