History NightmareFuel / StarTrekDeepspaceNine

** Winn in general has many shades of this, mostly in the fact that she is a very real, very mundane evil - the evil of zealotry. She dresses it up in the robes of the cloth, attaining the rank of Vedek before her introduction, and ends up elevated into the highest position in the Bejoran religion, a religion that most Bajorans we meet in the franchise have some level of belief in, is frequently consulted on matters of politics, even attempts to take the political position of First Minister at one point. And it cannot be argued that she is a zealot - her introduction featured her as a conspirator, plotting to lure a rival out in the open in order to assassinate him, and then abandoned her catspaw to the wolves once the effort failed. And it's what makes her turning from the Prophets all the more chilling - the Prophets, in not speaking to her after the message from the Pai-Wraiths, are conveying that she must step down from the position as Kai. So, when faced with the decision of following the religion that she has devoted her life to and has reached the ascendancy of, or turn from them, embrace their devils, and hold on to power... She cannot conceive of surrendering power. If her gods won't give her power, if they don't want her to retain it, then she denounces them for ones who will.

* The Breen. They only appear in a handful of episodes, but they [[OneSceneWonder certainly make an impact]]. For one, their technology is different, more advanced, than anything the Alliance has, able to destroy the ''Defiant'' in only five minutes. Second, we know NOTHING about them; their culture, motives, even what they look like under those suits, all are left mysterious. And finally, ''we don't even know what they're saying''. The Universal Translator seems to translate their speech, but it's all R2-D2 Speak to the audience. All we take from them is what we see: they're clever, [[ChaoticEvil unpredictable]] killing machines with [[TheUnfettered absolutely zero mercy]]. The Breen ''epitomize'' NothingIsScarier.

* In ''The Jem'Hadar'', the titular aliens attack a '''retreating''' Galaxy-class starship (the same class as the ''Enterprise'' from TNG). And the Jem'Hadar destroy it by [[RammingAlwaysWorks ramming it]]. All to send a message to the Federation, the war goes downhill from there.

** Cranked UpToEleven in "Empok Nor", when you find out just how terrifying Garak really is once you take away the smiling façade. The whole episode is a horror movie in space.

* The Founder showing actual fury at the realization that the Cardassian people are raising up against the Dominion. In a very casual grip, she grabs Legate Broca (the token Cardassian functionary who is more of a Dominion puppet than Damar ever was) by the throat and casually condemns the lives of everyone in Lakarian City to death - and reminds the viewer how dangerous a Changeling can be, even if they are unable to shapeshift.

* Number three for O'Brien's suffering on the page, we have "Whispers". Long story short, the O'Brien narrating the episode is actually a clone, who is killed at the last minute of the episode. The terror is that ''no one'' realizes just how perfect a clone he was. Except for the mental command to attack a senator, the clone!O'Brien is in no way different from the real one. Same memories, same emotions, and with ''no'' evil tendencies. He's just... killed. Unceremoniously. No one in the room cares that he's dying. He did absolutely nothing to deserve his fate. In fact, his efforts to prevent the attack (he didn't realize that ''he'' was the one who was supposed to carry it out) are extremely heroic. Dying scared, confused, and alone.

** Winn in general has many shades of this, mostly in the fact that she is a very real, very MundaneEvil - the evil of zealotry. She dresses it up in the robes of the cloth, attaining the rank of Vedek before her introduction, and ends up elevated into the highest position in the Bejoran religion, a religion that most Bajorans we meet in the franchise have some level of belief in, is frequently consulted on matters of politics, even attempts to take the political position of First Minister at one point. And it cannot be argued that she is a zealot - her introduction featured her as a conspirator, plotting to lure a rival out in the open in order to assassinate him, and then abandoned her catspaw to the wolves once the effort failed. And it's what makes her turning from the Prophets all the more chilling - the Prophets, in not speaking to her after the message from the Pai-Wraiths, are conveying that she must step down from the position as Kai. So, when faced with the decision of following the religion that she has devoted her life to and has reached the ascendancy of, or turn from them, embrace their devils, and hold on to power... She cannot conceive of surrendering power. If her gods won't give her power, if they don't want her to retain it, then she denounces them for ones who will.

* The Founder showing actual fury at the realization that the Cardassian people are raising up against the Dominion. In a very casual grip, she grabs Legate Broca (the token Cardassian functionary who is more of a Dominion puppet that Damar ever was) by the throat and casually condemns the lives of everyone in Lakarian City to death - and reminds the viewer how dangerous a Changeling can be, even if they are unable to shapeshift.

* "Strange Bedfellows" ends with Kai Winn turning away from the Prophets and choosing the Pah-Wraiths. Throughout her previous appearances, she's been a BitchInSheepsClothing who acts with HolierThanThou SugaryMalice that's creepy enough, but her final speech in this episode casts all of that away and shows her true self-serving, egotistical darkness.

* Another 'O'Brien must suffer' episode, 'The Assignment', brings us the very memorable first appearance of the Pah-Wraiths. One of them possesses Keiko and uses her as a hostage in an efficient and sadistic manner that's all the more unsettling for how ''casual'' it is. The sequence where the Wraith calls O'Brien about his rapidly-approaching deadline whilst combing Molly's hair is pure AdultFear.

* In "Statistical Probabilities", the Jack Pack, a group of highly intelligent genetically-engineered humans, give us their long-term projections for the Dominion War: [[HopelessWar The Federation has no chance of winning]] and ''900 billion'' people will die if the conflict continues. As such, the only smart thing to do would be immediate surrender. They determine that, after five generations of Dominion rule over the Alpha Quadrant, an Earth-based rebellion will overthrow them and establish a stronger Federation...the very same conclusion that Dukat and Weyoun reached a few episodes earlier, and the reason Weyoun concluded that [[FinalSolution the Dominion should completely sterilize earth after their victory]].

** For that matter, his willingness to kill (or indeed, allow people to die) to resolve a situation always horrifies the people around him, even those (like [[YourTerroristsAreOurFreedomFighters Kira]] ) who are used to death and using killing to attain a goal.

* Number three for O'Brien's suffering on the page, we have "Whispers". Long story short, the O'Brien narrating the episode is actually a clone, who is killed at the last minute of the episode. The terror, as pointed out by WebSite/SFDebris, is that ''no one'' realizes just how perfect a clone he was. Except for the mental command to attack a senator, the clone!O'Brien is in no way different from the real one. Same memories, same emotions, and with ''no'' evil tendencies. He's just... killed. Unceremoniously. No one in the room cares that he's dying. He did absolutely nothing to deserve his fate. In fact, his efforts to prevent the attack (he didn't realize that ''he'' was the one who was supposed to carry it out) are extremely heroic. Dying scared, confused, and alone.

** And it's not just about sending a message either. As we learn later, Jem'Hadar and Vorta are extremely easy to replace and the founders do not regard their lives as valuable. This means they can afford to think of strategy like they're playing a game all the time. As long as the other guy loses more than they do, the engagement is a success.

[[caption-width-right:350: ''This'' is why you shouldn't let a Changeling hold their shape for more than 16 hours.]]

-->'''Darhe'el''' [[spoiler: (actually Marritza)]]: Oh, no, no, Major, you can't dismiss me that easily. I did what had to be done. My men understood that, and that's why they loved me. I would order them to go out and kill Bajoran scum, and they'd do it! They'd murder them! They'd come back covered in blood, but they felt clean! Now why did they feel that way, Major? Because they ''were'' clean!
** The fact that there is a man like [[spoiler: Marritza. It is easy to see the Cardassians are evil and wicked, as monsters who invaded Bajor and murdered its people. But Marritza forces Kira and the audience to realize there were victims on their side too... people too scared to do something and now tortured with the knowledge of what happened. How many other 'weak, whimpering' Cardassians are out there, haunted by the pleas of the Bajoran children...]]

* Number three for O'Brien's suffering on the page, we have ''Whispers''. Long story short, [[spoiler:the O'Brien narrating the episode is actually a clone, who is killed at the last minute of the episode.]] The terror, as pointed out by WebSite/SFDebris, is that ''no one'' realizes just how perfect [[spoiler:a clone]] he was. Except for the mental command to attack a senator, [[spoiler:the clone!O'Brien is in no way different from the real one. Same memories, same emotions, and with ''no'' evil tendencies.]] He's just... killed. Unceremoniously. No one in the room cares that he's dying. He did absolutely nothing to deserve his fate. In fact, his efforts to prevent the attack (he didn't realize that ''he'' was the one who was supposed to carry it out) are extremely heroic. Dying scared, confused, and alone.

* The Breen. They only appear in a handful of episodes, but they [[OneSceneWonder certainly make an impact]]. For one, their technology is different, more advanced, than anything the Alliance has, able to ''[[spoiler: destroy the Defiant in five minutes]]''. Second, we know NOTHING about them; their culture, motives, even what they look like under those suits, all are left mysterious. And finally, ''we don't even know what they're saying''. The Universal Translator seems to translate their speech, but it's all R2-D2 Speak to the audience. All we take from them is what we see: they're clever, [[ChaoticEvil unpredictable]] killing machines with [[TheUnfettered absolutely zero mercy]]. The Breen ''epitomize'' NothingIsScarier.

* In "The Darkness and the Light", in which someone is killing Kira's resistance cellmates, they send her messages saying "That's one", etc. as each person is killed, in a deeply creepy Saw-type distorted voice. Even creepier? [[spoiler:They use Kira's voice.]]

* In "Field of Fire", when the [[spoiler:insane Vulcan]] murderer is revealed, he says he committed his crimes [[spoiler:because it was ''logical'']].
** Another creepy moment happens [[spoiler:when Ezri and the villain, both using guns which can see through walls, '' find themselves aiming at each other, at the exact same time, from all the way across the freaking station]].''
** Also, their weapons, the TR-116: [[spoiler: guns that can see through walls, have integral silencers, and, with a small modification, can ''teleport bullets''.]]
*** And if you think it's bad, let's add FridgeLogic: [[spoiler: as the miniature transporter attachment isn't readily apparent, O'Brien was apparently aware of it, and the sensors could be useful only for that, there are strong hints it was ''intended'' to act with the transporter]]. Then, let's examine another feature of the gun: [[spoiler: it used large 9-10mm subsonic rounds, too slow and short-ranged for combat use without the transporter attachment (that could be easily jammed in combat condition) and large enough that the magazine could only hold 2-3 of them at a time. What can you use a short-ranged sniper rifle with pistol-caliber teleporting ammunition and a small magazine whose transporter can be easily jammed? Hostage situations... Or assassinations.]] [[BewareTheNiceOnes And it was built by the Federation]]. Let's just hope the [[spoiler: transported attachment]] ''was'' an addition to the design and the [[spoiler: sensors that can see through the walls]] were just added by a designer showing off...

* TheReveal that the [[ShapeShifter Changelings]] [[spoiler: had infiltrated the Federation]]. "It's too late; [[WeAreEverywhere we're everywhere]]."

* The Founder showing actual fury at the realization that the Cardassian people are raising up against the Dominion. In a very casual grip, she grabs Legate Broca (the token Cardassian functionary who is more of a Dominion puppet that Damar ever was) by the throat and casually condemns the lives of everyone in Lakarian City to death - and reminds the viewer how dangerous a Changeling can be, even if they are unable to shapeshift.

** More subtle than Empok Nor, and all the more terrifying for it, is Garak's handling of Tolar, the holo-forger from "In the Pale Moonlight." The episode makes much of Garak's assassination of Vreenak, a Romulan senator, but for that Garak required Sisco's full, albeit unwitting, cooperation. In contrast, Garak "disappeared" Tolar, off-screen and without attracting attention from ANYONE, not even Odo, over the course of two days. It's only realized he did so when Sisco makes the disturbed inference that this side of Garak would never allow dangerous witnesses to live past their usefulness.
** Garak did get this himself earlier in the episode when Sisko wants him to use his old contacts on Cardassia to get some information. Garak reaches out to spread the word...and just ''one day'' after talking to him, ''every'' one of his contacts is dead. While he tries to be light talking about it, it's clear Garak is rocked that just ''knowing'' him constitutes a death sentence on the Dominion-run Cardassia. Although it's {{Implied}} that Garak was just saying this to [[XanatosRoulette manipulate Sisco]], that level of manipulation and intrigue carries its own Nightmare Fuel.

** The fact they just gave back the liberated worlds as soon as Federation and Klingons showed up to reclaim them isn't scary... Until you realize ''why'' they did it: to show they can take them back whenever they want ''next war''.

-->'''Odo:''' Interesting, isn't it? The Federation claims to abhor Section 31's tactics, but when they need the dirty work done, they look the other way. It's a tidy little arrangement, wouldn't you say?

* In "The Dogs of War", Odo's sheer unbridled ''fury'' at the Federation allowing Section 31 to unleash their tailored plague on the Founders, and moreover using ''him'' as the carrier to infect the Founders through the Great Link. Worse, when he goes to Sisko for an explanation, the captain uncomfortably tells him that while the Federation Council objected to Section 31's actions, they won't give the Founders the cure because they're afraid it will prolong the war. That the idealistic Federation we have come to know and love has come to this after two years of war with the Dominion is downright ''chilling.''

* Tribunal, being another "O'Brien must suffer" episode has the scene where, after being taken prisoner by the Cardassians, O'Brien is "processed", for a crime he has supposedly committed (except no one will tell him what that crime ''is''). He is ordered to [[ShamefulStrip remove his clothes]] and when he refuses, instead stating his name, and rank, and asserting he is a Federation citizen, he is forced against the wall by two guards who proceed to forcibly rip his clothes off him. He is then forced onto the floor where a retinal scan is taken (and from O'Brien's reaction, it's suggested the scan is painful) before he is dragged to a rather sinister-looking operating table. He briefly tries to escape but is punched in the face by a guard and restrained. Then he appears to be drugged with some sort of hypospray, while a lock of his hair is cut off and a tooth is forcibly removed, without the use of anesthetic. It's even more graphic and unpleasant to watch than what Picard went through with Gul Madred in TNG, and this is before we even get to the mockery of justice that is [[KangarooCourt Cardassian jurisprudence]]. Earlier in the season, during The Maquis two-parter, Dukat had arrogantly boasted about the "perfection" of the Cardassian legal system (that the verdict is always decided beforehand, it's always guilty, and that "trials" are really nothing more than scripted televised farces designed to show the terrifying power of the Central Command, and also, it's implied, as a twisted form of entertainment for the public who enjoy seeing "justice triumph over evil") except now we actually get to see how terrifying this system actually is.

** It also makes the plot of ''Duet'' make sense in a rather sickening way- Maritza thought that he would have a Cardassian style trial, where he would be told "You're guilty, send him to the execution!" After pointing out all of his crimes, of course, which would expose the cruelties of Cardassia to the Alpha and Beta Quadrants. In a way, it makes it far more heartbreaking what actually happened- he expected he'd only need to keep up the charade for a short time, and his already broken mind shattered completely once the ruse was exposed. He went there to die, to be free of the nightmares... but they didn't play according to the rulebook he knew...
* Q's simulation/reenactment in [[https://tvtropes.org/pmwiki/pmwiki.php/Recap/StarTrekDeepSpaceNineS01E07QLess Q-Less]] of what would have happened to Vash from her insect bite if he hadn't cured her. Seems unusually cruel for Q (at least to [[https://tvtropes.org/pmwiki/pmwiki.php/Recap/StarTrekTheNextGenerationS3E13DejaQ humanoids]]), even if he was about to cure her again.

* In "The Dogs of War", Odo's sheer unbridled ''fury'' at the Federation allowing Section 31 to unleash their tailored virus on the plague, and moreover using him as the carrier to infect the Founders through the Great Link. Worse, when he goes to Sisko for an explanation, the captain uncomfortably tells him that while the Federation Council objected to Section 31's actions, they won't give the Founders the cure because they're afraid it will prolong the war. That the idealistic Federation we have come to know and love has come to this after two years of war with the Dominion is downright ''chilling.''

* Tying in to the above mention of Vedek Yasim's suicide, we have Kira's realization in that episode - the Dominion and Cardassians may not have reopened the ore processors, Bajorans may not be executed in the street on the whim of a Cardassian, the labor camps haven't reopened, but this is still an occupation, and, as she sits there, as invaders walk outside her door, as the Federation and Klingons fight the Dominion on multiple fronts (and having to retreat from them), her inaction makes her a collaborator. It's a perfect encapsulation of the sheer mundanity of evil - the more you're surrounded by it, the more you're inured to it, the less it fazes you, the less action you feel you need to take. It's chilling to realize how passive and numb one can become when, day in and day out, you're faced with these horrors, and, as it goes on, it just stops impacting you and you go about your business.

* In one episode, Sisko is trapped on a planet with Dukat, who's having hallucinations--imagine, being trapped on a (probably uninhabited) planet with a sadistic villain who is also hallucinating. Yipes!