[[quoteright:180:[[TabletopGame/{{Warhammer 40000}} http://static.tvtropes.org/pmwiki/pub/images/fabius_bile_854.jpg]]]]
[-[[caption-width-right:180:The doctor will see you now.]]-]

->[[DarkestHour Have we exhausted all possible ways to divine the future]]? [[FailureIsTheOnlyOption How many scribes must toil to scratch their visions onto ancient parchments so that we might catch a glimpse of hope]]? [[DespairEventHorizon Or are we to suffer only the pangs of despair as yet more horror is let loose on our dreams]]? [[GoMadFromTheRevelation Or does the seeking itself give birth to more insanity than man can cope]]?

->[[FreakOut The Dark Future Beckons]]!

->[[DrivenToMadness Fear the Unknown]]!
-->-- ''Warhammer 40,000''

As the origin of the term [[DarkerAndEdgier Grim Dark]], it's no surprise that ''TabletopGame/{{Warhammer 40000}}'' is a setting positively ''drowning'' in horror. [[NightmareFetishist And we wouldn't have it any other way]].

----

* In brief, the whole game. On this page, we have named every fighting force, every faction, some of the most significant aspects of the setting, the resident death worlds, and even a food production plant. It's a brutal, horrific place, with more atrocities in a year than we see in a millennium, but remember that in Warhammer 40000, [[TheExtremistWasRight almost all of the evil on the part of heroic characters and factions is necessary given]] [[CrapsackWorld the world they live in.]] Or at least, there have been enough instances where TheExtremistWasRight that the "ask questions" part of "shoot first and ask questions" was forgotten. That should tell you something about what you're about to find.

[[foldercontrol]]

[[hardline]]

!The Forces of Chaos

[[folder:'''Nurgle''']]
* '''Nurgle''' loves his followers, he really does. And he'd probably be jolly good grampy to you, if you'd just join up. It just so happens he shares his love by [[BodyHorror infecting you with so much disease]] you end up a bloated rotting zombie-like thing which is in so much pain that it can't feel ''any other pain''. But Papa Nurgle loves you, so it's ''all fine''.
** ''And they love it''. Other servants of Chaos are intensely suffering or blindingly insane or "merely" a mindless spawn, but Nurgle followers genuinely enjoy being followed by clouds of plague flies and having their organs dragging on the ground, and nothing would please them more than giving you a biiiiig hug so you can enjoy it too. Come to Papa Nurgle~
*** It is similar in some ways to Literature/NineteenEightyFour, where all citizens get to be brainwashed by the oppressive Party and end up ''worshiping the very organization that has made their lives miserable''. Sure, the specifics of the methods to that result may be different, but still, Nurgle [[MindRape tampers with your mind]] and transforms you into a mindless zombie drone worshipping ''diseases''.
** And yes, it ''still'' gets worse. [[TheVirus Nurgle's Rot]], perhaps the most gruesome of the nightmarish Chaos powers, infects almost all of his followers and can be transferred with a single touch, inflicting the poor victim with a concoction perfected by Nurgle himself to cause the most agony while still keeping them from death, many pledging themselves to Nurgle just to end their suffering. It also [[{{Brainwashed}} contaminates the soul]] [[ViralTransformation as well as the body]], each person killed by the Rot [[YouWillBeAssimilated creating another Plaguebearer]] in Nurgle's "garden", the more they resist death merely resulting in a more powerful Plaguebearer. Oh, and said garden may include one very special favored guest, who Nurgle force-feeds all his creations to just to see how powerful and harmful they are...
** Who is the above special guest? The only being able to cure Nurgle's creations, Isha, the goddess of life. [[AbhorrentAdmirer Who Nurgle is trying to convince to marry him.]] And she's ''still'' better off than with her previous "suitor," Slaanesh, about whom see below. But since she can cure any of Nurgle's creations, that means she cannot die, so the experiments will ''never'' stop.
** Plague Marines. Dark, bubbling, deep, filthy, scary...
---> We...''[gasp]''... are '''''Death'''''... ''[rasp]'' and '''''Decay'''''... ''[wet gagging]''...
** The Death Guard. Take the best qualities of the Space Marines, combine them with ''28 Days Later'' style zombies, and you'll have something akin to a Death Guard trooper. Scariest of all (both in tabletop and in fiction), they are {{Determinator}}s - they'll never stop coming at you until you're either a festering mass of plague or dead. And the Plague Marines? The Death Guard is basically an entire Legion of them.
** Beasts of Nurgle are abhorrent, sluglike creatures dripping with toxic ooze, spurting dangerous gases from chimneys on their back and dribbling acidic spittle. But these things are not insane, dribbling wrecks- they have the minds of cute, playful puppies, who only wish to give the enemy bone-crushing hugs and slobber all over them. As if this wasn't bad enough, they have no concept of death - once they kill, they are momentarily disappointed by the fact [[AndCallHimGeorge their new playmate has gone still]], then ooze over to another foe to make a new friend.
** The Rot Flies of Nurgle. Sometimes, a Beast of Nurgle starts ''resenting'' that all its human playmates either won't play or actually chase it back to the work. And that resentment just builds and festers until the Beast spins a cocoon and pupates. What hatches is a monstrous, plague-ridden, slime-dripping fly-daemon that is now actively malicious and cruel. They favor going for the heads of their enemies; either snipping them off with giant mandibles or using a disgusting proboscis to ''suck their victim's head so hard they slurp out the entire spine in one gulp''. They digest these skulls inside their foetid bellies and then spit them as projectiles. But some people, they hold a special grudge against. These people? The Rot Fly ''swallows them whole'', trapping them inside its worm-riddled, stinking, pustulent guts ''forever''.
[[/folder]]

[[folder:'''Khorne''']]
* '''Khorne'''. He'll give you [[OneManArmy martial might beyond compare]], [[{{Determinator}} a will to dominate that knows no bounds]]... which translates into [[TheBerserker frothing berserker strength]]. All he asks for is blood. Lots of blood. [[FriendOrFoe Your enemies', your friends']], ''yours'' - he isn't picky. Khorne cares not from whom the blood flows, only that it does.
** His Greater Daemons, Bloodthirsters, are the most feared beings in an entire galaxy of [[EarthShatteringKaboom planet-crushing]], [[HorrorHunger soul-eating]], [[TheJuggernaut unstoppable monstrosities]]; even the Grey Knights are wary to speak the names of the most powerful ones. Invigorated by the might of Khorne himself, their [[SuperStrength martial prowess]] exceeds all but the Primarchs, and they are [[PersonOfMassDestruction more than capable of crushing armies]] [[PhysicalGod and rendering planets barren]], more often than not leading their own army of ravenous daemons that share their desire for blood and carnage.
*** Ever heard of {{Doom|yDoomsOfDoom}}breed? A Daemon Prince from the Dark Age of Technology, recruited by Khorne in his younger days. FridgeLogic assumes him to be any one of a number of RealLife warlords, unless he has [[WorldWarIII yet to be born.]] [[FridgeHorror Which is probably worse.]]
[[/folder]]

[[folder:'''Tzeentch''']]
* '''Tzeentch''', god of [[TheChessmaster chessmasters]], {{manipulative bastard}}s, and the GambitRoulette. He'll grant you [[BlackMagic sorcerous]] {{p|sychicPowers}}owers beyond your wildest dreams, [[DreamingOfThingsToCome visions of the future]], and [[MagnificentBastard the ability to craft schemes of dizzying complexity]]. Unfortunately, he's called the Changer of Ways for a reason, so you might [[LovecraftianSuperpower get a mutation. Or two. Or twenty.]] Since Tzeentch is above all else a god of [[TheCorruption Chaos]], despite his patronage [[DidntSeeThatComing your schemes may fall apart]], especially if your mutations go so out of control you regress into a mewling, mindless Chaos Spawn. But don't worry. [[GambitPileup That was part of his plan all along]].
** The Thousand Sons Legion learned this [[UnwittingPawn the hard way]]. Soon after being banished to the [[NegativeSpaceWedgie Eye of Terror]], all of them began accumulating so many mutations that some weren't so much "unrecognisable" as "oh god oh god what the hell is that". Their most powerful [[EvilSorceror sorceror]] Ahriman cast a massive spell in an effort to prevent certain destruction, and he succeeded in halting the mutations... by converting most of the Legion to dust and sealing them inside their armour forever, transforming them into [[MechaMooks mindless automata]]. However the spell also turned the [[BlackMagic sorcery]] of the minority with even a little psychic power UpToEleven, so it's all good.
*** The best part is that the Thousand Sons primarch turned to Chaos (and Tzeentch) to save his legion from extermination. At the end he learns that Ahriman's fiasco was all part of Tzeentch's plan.
*** Every time the Thousand Sons commit some sort of atrocity, remember this: Primarch Magnus the Red tried to ''warn'' the Emperor of Horus' treachery via sorcery, which the Emperor didn't like so much, and thought that his favorite Primarch betraying him was preposterous. Instead, he believed ''Magnus'' was trying to betray him and sent Leman Russ to "arrest" him and bring him to Terra. Sure, Horus convinced Russ to try and kill Magnus, but considering how the Space Wolves regard sorcery, this was about as good an idea as sending a lynch mob to arrest a child rapist.
** Also think about the Tzeentchian Greater Daemons, the Lords of Change. They have the power to rip souls from the strongest of men with but a glance, tear tanks in half with their immense magical knowledge, and many mortals mistake them for being ''omniscient'' from all that they know about virtually anything. And worst of all is that they can see into the immediate future because Tzeentch sends it to them, so they're nearly impossible to kill. And if you ''do'' kill one? That's only because Tzeentch sent it ''false'' images of the future and ''let'' you kill it. Congratulations: you just furthered the plans of Tzeentch.
** Another Greater Daemon of Tzeentch is Fateweaver, once the most powerful of Tzeentch's Lords of Change...until Tzeentch hurled him into the Well of Eternity, where the events of all time both begin and end, in an effort to gain ''perfect'' knowledge of all things. This had ''killed'' every Lord of Change prior to Fateweaver, and reduced him to a hunched and weakened shadow of his former self. It even forced the growth of a second head, and both heads answer any question asked of Fateweaver. One will be the truth, the other an equally believable lie. Tzeentch has a few dozen Lords of Change on hand to record ''every word he says'' just to make sure they don't miss anything.
** And the Changeling, who has such absolute control over his ability to shapeshift that he's lost his original form. Only Tzeentch knows what it is, and he doesn't tell him to keep his control over him. That doesn't stop him from being an exquisite MagnificentBastard in the name of Tzeentch. Once, a rogue Imperial governor summoned the Changeling and asked for an artifact to break the siege that the Dark Angels were laying upon him. The Changeling handed him a device, then vanished...and was replaced by a squad of Terminators. He'd handed the governor a teleport homer. Broke the siege, though not the way the governor wanted.
** And do you know what Tzeentch's ultimate plan is? ...[[spoiler: '''He doesn't have one!''' Tzeentch is the very embodiment of scheming and change and transformation; he doesn't ''need'' a goal to achieve. He exists, literally, just to meddle with things and see what happens; he can never lose because he's not trying to ''win''. No matter what the outcome is, so long as something keeps happening, Tzeentch is winning -- he's just got to set the wheels in motion so that the universe keeps changing.]]
*** [[spoiler: In a way, that's a bit (however tiny) of good news for everyone else, because if he did have some ultimate diabolical goal (such as enslaving the souls of ALL humanity at once), he could easily do so since he obviously has the power and especially foresight for it. Thank the Emperor that he's too "random" for that.]][[/folder]]

[[folder:'''Slaanesh''']]
* And then we have '''Slaanesh''', the Dark Prince of Pleasure. [[AmbiguousGender (S)he'll]] give you sensations beyond your imagination, [[SexIsEvil pleasures]] and [[TooKinkyToTorture pain]] beyond mortal understanding... which your warped body will eventually become acclimated to, [[SenseFreak forcing you to take increasingly extreme measures to reach similar highs]], even as your senses become dull. Eventually you'll be undertaking ever-more disgusting atrocities in an attempt to stir your jaded emotions, while you hardly feel anything at all...
** The Emperor's Children Legion serves Slaanesh exclusively, and are essentially SuperSoldier versions of Dark Eldar as a result. During the siege of Terra, when the other Legions were assaulting the Imperial Palace, they decided their time was best spent killing millions of the planet's inhabitants to convert them into [[PsychoSerum the various drugs that composes about fifty percent of their bloodstream]], thousands more slaughtered to [[FateWorseThanDeath provide more... direct pleasure]]. In the ten thousand years since then they have performed more successful raids than any other Legion, devoted not to revenge or conquest or conversion but to [[TheHedonist simple pleasure]]. And unlike the Dark Eldar, they don't do it to prevent their soul being eaten; they just love it.
** And then there's [[DemonicPossession what]] [[EvilWeapon happened]] [[TheCorruption to]] [[AndIMustScream Fulgrim]]. See, sometimes the deamon won't just jump into one's head and take over. If it's Slaaneshi there's a good chance it will first have some fun with you. In Fulgrim's case, first it dug out all of his insecurities and convinced him his best friend was jealous of him. Then it convinced him to kill his best friend, and then ''[[DespairEventHorizon it showed him that said best friend had been trying to save him all along]]''. And then it didn't destroy Fulgrim's mind, because it wanted him to watch what it would do, 'cause his suffering would be fun.
** Oh, and that "previous suitor" of Isha under Nurgle's section? That's Slaanesh. One wonders which is worse for a goddess of healing: being the captive of the god of sadomasochistic hedonism, or of the god of pestilence and decay.
*** At least Nurgle was rescuing her, which is saying something. He was able to do so while Slaanesh was busy slaughtering the rest of the Eldar pantheon. And she uses her position to whisper cures to Nurgle's diseases to mankind.
** All of the Chaos Gods have Chaos Marines devoted specifically to them. Slaanesh's are the Noise Marines; {{Sense Freak}}s so jaded and burnt out that they can't "feel" anything any more. So they take to the battlefield wielding [[MakeMeWannaShout sonic weaponry]], because the resultant cacophony is the only thing that can provoke any reaction in them any more. These have absolutely horrific effects on anyone they hit with them -- imagine a sound so [[BrownNote intense]] that your flesh literally ''melts off your body from the vibrations''. These even managed to be creepy when the official models for them sported [[MusicalAssassin weapons designed to resemble guitars and electric keyboards]].
** A Slaaneshi Lord.
--->[[http://wh40k.lexicanum.com/wiki/Quotes_Chaos#T ''Take care, lest your protests grow tiresome. I have asked for so little! Anyone would think that I have asked you to sacrifice yourselves and your sons! And yet, in Slaanesh's boundless and pleasing mercy, I have asked only for your daughters. Surely you would not deny me my small enjoyments?'']]
[[/folder]]

[[folder:'''Malal''']]
* The outcast chaos god, '''Malal''', God of Destruction. [[EveryoneHasStandards Yes, there's a Chaos God so bad that even the other Chaos Gods won't associate with him.]] Mentioned in early ''Warhammer'' fluff (including a series of comic books) and then stricken from the setting for copyright reasons, Malal favors single, powerful worshipers rather than armies, and has a special place in the Pantheon -- [[PayEvilUntoEvil he hunts down the other chaos forces.]] Yes, Malal is the chaos god of all destruction, including ''self destruction'' -- his modus operandi is to pick one particularly powerful chaos champion, [[SpannerInTheWorks insert him in the exact right spot to cause as much trouble as he can for the other four]], and then empower him with as much of his own energy as he can get away with -- something that he steals back, [[CastFromHitPoints with interest]], from the worshiper. The resulting carnage is one of the only things keeping the other four chaos gods at bay.
** While Malal has been stricken from the fluff, the most recent Chaos army books have added The Sons of '''Mal'''ice[[note]]Malal is an Eastern Indian word for Malice[[/note]], a special Chaos Space Marine army with Malal's color scheme. The story behind the SOM is horrifying in and of itself -- they were particularly loyal Space Marines from a somewhat feral world, except that they had a specific knack for [[NothingIsScarier fighting in complete and utter silence]], and their home planet had a thing for [[{{Gorn}} especially]] [[ImAHumanitarian gory]] victory celebrations. A particularly puritanical Inquisitor happened to watch one of these celebrations, and while completely ignoring the similar rituals of other, more established (and thus, protected against a single inquisitor going against them) chapters, had them personally declared traitors and their homeworld {{de|populationBomb}}stroyed -- something that is heavily insinuated could happen to any other loyalist chapter who happens to get the wrong Inquisitor visiting them -- in fact, it's implied that the only thing that caused the Sons of Malice to fall was the fact that ''they didn't kill the Inquisitor fast enough.'' In other words, the Sons of Malice and the millions of people living on their homeworld were screwed over by the ''Warhammer 40000'' version of an ObstructiveBureaucrat.
** It's more violent than most cannibalistic chapter rituals. In the short story The Labyrinth from Heroes of the Space Marines, they are depicted eating slaves alive. The rest of The Labyrinth is quite scary, what with the BodyHorror of the transformed marines and [[spoiler: it ends with the protagonist, having run the titular Space Hulk's gauntlet, being sacrificed with the ten other victors to summon Malice (renamed due to copyright) himself.]]
[[/folder]]

[[folder:'''The Chaos gods in general''']]
* The worse part about all 5 Chaos gods? All Chaos gods can be taken as corrupted versions of otherwise positive emotions:
** Slaanesh as a corruption of Love or Happiness. As long as someone loved another, they're contributing directly to Slaanesh. And if they loved even a bit too much, they may be approached... and the corruption shall begin...
** Khorne as a corruption of Bravery or Glory. In the [[DarkerAndEdgier Grim Dark]] universe where there is only war...
** Tzeentch as a corruption of Hope or Wisdom. Any who hope for deliverance, any who wish to learn more to make a better tomorrow, they will fall into Tzeentch's clutches...
** Nurgle as a corruption of Acceptance or Friendship. Friendship is pretty much guaranteed between people, while... "Acceptance" sounds familiar? It is the central dogma of most of the uncountable masses of the Imperium...
** Malal is a corruption of '''Justice.''' It's specifically stated that anyone who hunts Chaos too effectively, anyone who lets the hunt consume them, has a chance of being approached by Malal.
* In other words, ''even if you win against Chaos, you still lose.''
* In the ''HorusHeresy'' novella ''Aurelian'', Ingethel the Ascended tells Lorgar, whose Legion masterminded the Horus Heresy, that those who worship the Chaos Gods will be accepted into their power, and those who reject the Chaos Gods will be devoured by daemons. This concept of the afterlife is a major part of Chaos Undivided, and is why the Word Bearers pride themselves on knowing the truth. Unfortunately, it's also BlatantLies. In ''Deliverance Lost'', during the aftermath of the Drop Site Massacre, a Word Bearers vessel trailing the Raven Guard's last battle-barge gets pulled into the Warp. Do those within, who have dedicated their lives and souls to the Chaos Gods, get taken to a pleasant afterlife? No. They're devoured and tormented by daemons just as much as someone who rejects Chaos. There's a reason Chaos is dubbed "The Bad Guys" of the series. It's because the Chaos Gods literally don't give a damn about their followers.
* The Chaos Gods themselves represent corrupted Chaos, not just chaos itself. As mentioned elsewhere, Chaos is affected entirely by the emotions of sentient beings in real space. Ever wonder why Chaos is ChaoticEvil and not ChaoticGood or ChaoticNeutral? It's because that the galaxy and every living thing in it are just ''[[CrapsackWorld that screwed up]]''. The fact that all factions are AxCrazy, {{manipulative|Bastard}}, [[AbsoluteXenophobe xenophobic]], {{omnicidal|Maniac}}, is why Chaos is the absolute worst of all of them. No one will ever "win" ''Warhammer 40000'', because evil itself exists and it has already won. It won a long time ago...
** Although canonicity can be [[DependingOnTheWriter somewhat fluid]] and subject to retcons, there is a general timeline that shows three of the current Chaos Gods coming into full being somewhere between the eighth and fifteenth millennium. This is also the time-frame when Mankind first began to prolifically expand into the stars, and saw an unprecedented boom in population numbers. Before this point, the Warp was of course Chaotic, but good gods (such as the Eldar pantheon) existed as often as evil ones. After this point it became infinitely more hellish. Although not explicitly stated, it's implied that the current state of the Warp, and indeed the very EXISTENCE of three of the four gods, is [[NiceJobBreakingItHero explicitly the fault of Mankind]] due to our high Warp presence and tumultuous minds.
* Among all that, there is still one more lingering fact; those 5 named chaos gods are simply the ''most powerful of the chaos gods''. It's hinted that the Chaos Gods are no more different than their lackey Lesser Daemons, save for the fact that they are a thousand fold stronger than them. There are more daemons than those serving the above 5, meaning each of those has a candidate for the title of "Chaos God" of their aspect. They are either simply not as strong as the current 5, or have simply not cared enough to make an impact on realspace. Of course, that doesn't mean they won't. Some of the more pessimistic delvers of hidden knowledge have concluded that when the Emperor of Mankind dies (and he will) the resultant Fall of Mankind to Chaos will not only open a rift into the Warp ''the size of the entire Galaxy'' but will create the final and mightiest Chaos God, who will corrupt, torture and enslave all remaining sentient life as they descend en masse into a screaming, eternal hell. Sweet dreams.[[/folder]]

[[folder:'''Chaos Forces in general''']]
* ANY named Chaos character is going to be scary.
* '''[[MadDoctor Fabius Bile]]''' (pictured top). It's not the fact that he's [[EvilutionaryBiologist turned entire worlds into shambling horrors with his genetic experiments]], or that he has a ''lab coat made of human skin''... it's the fact that he spent thousands of years floating in the Warp, has pure Warp energy constantly pumped into him, and he still doesn't worship any of the Chaos Gods. In fact, he's stated that they have no more to [[DealWithTheDevil offer him]]. People aren't supposed to make ''bargains'' with the [[EldritchAbomination Chaos Gods]]. ''That is not how it works.''
* Try '''Typhus''', the Herald of Nurgle and Host to the Destroyer Hive - Warp Flies that can enter your body through any orifice and feast on your innards, multiplying as they do so, until your body actually explodes from the pressure of all the plague-carrying insects inside you. These things swarm around him and obey his every whim. The Death Guard turned to Nurgle (they were already Chaos) when Typhus becalmed them in the Warp and unleashed the Destroyers after PARALYZING them all, letting them watch their comrades' fate and knowing they were next.
** "As the Destroyer spread throughout the Death Guard fleet, bursting the guts of the hardy space marines, Typhus came uncertainly to his feet and spoke a single gurgling, phlegm-laced word: '' 'More.' '' With that word, the flies left their hosts broken and bloated, and entered Typhus’ body like a wave. He remained on his feet, but his body was a hive of pestilence ever after." Brrr...
** Ever notice how there's never a depiction of Typhus with his helmet off (there is one of him as Typhon, but none after his transformation)? It's because the transformation of his body into the Destroyer Hive ''smeared his body into his armor''. Under his Terminator Armor he's essentially a living, fleshy honeycomb; his skin long since fused to the inside of his armor.
* And '''Lucius the Eternal'''. If he thinks you're a worthy foe, he'll duel you. If he wins, you're dead. If he loses, you win, but if you feel even an ''instant'' of triumph or even mild satisfaction, you end up [[KarmicTransformation transforming into him]], being [[AndIMustScream bound to his armor]] while his [[DemonicPossession soul takes you over]].
** He's a member of the Emperor's Children, which means he's a SenseFreak on equine growth hormone. Even before the Horus Heresy he'd carved up his own face, linking up the scars of a lifetime of battle to make a jagged irregular pattern, and the first time he lost a duel the codex specifically says, "Lucius' agonizing death was an experience of transcendent pleasure." So he's basically [[{{Franchise/Hellraiser}} Pinhead]] as a Space Marine with a thing for dueling.
* '''Angron''', Daemon Primarch of the World Eaters Legion. For one of the handful of times one of the Primarchs returned to the material realm, he descended upon the planet of [[MeaningfulName Armageddon]] following an endless stream of daemons and proceeded, to use the vernacular, to ''fuck shit up''. An entire 100-man company of Grey Knight Terminators, the very elite of the Grey Knights themselves, who are arguably ''the'' greatest Space Marine Chapter in the Imperium specifically trained to [[DemonSlaying fight daemons]], were deployed in response, and '''almost all''' of them died, succeeding only in banishing him back to the Warp for 100 years (and a day), at which point he might decide to try slaughtering millions again "for the Blood God". Before he had been banished, he ravaged Imperial space for ''two centuries''. Angron and his force took over '''seventy sectors''' in what was known as the "Dominion of Fire" and it took a force of four Space Marine ''Chapters'', thirty Imperial Guard ''regiments'', and two ''Titan Legions'' to recover what was lost.
** According to 4th Edition, it took said chapters/regiments/legions about three millennia to retake 90% of the conquered territories (Angron's previous up-fucking of shit occurred in the middle of the 38th Millennium).
* And '''Kharn''', nicknamed the Betrayer, is probably the most batshit AxCrazy of of them all. Here is the man who, in a fit of anger, ''singlehandedly shattered his own Leigon's capacity as a fighting force with nothing but a flamethrower''. The game reflects this - he's just as likely to go bonkers and start hacking apart his own men if he feels like it. You have been warned.
** It gets "better"--he also shattered another legion at the same time. The two legions--the World Eaters and the Emperor's Children--were fighting over a daemon world called Skalathrax, and both sides called a temporary cease-fire in light of deathly cold nights on the planet. Kharn, of course, was having none of that, and decided to burn the shelters that had been taken to force both sides fight both enemies and their brethren alike to get place in remaining shelters simply to survive. Ultimately, the legions were fragmented into warbands, and Kharn has since become the embodiment of Khorne's indiscriminate rage.
*** To drive home how [[UnstoppableRage invincibly angry]] Angron is, Kharn (aka the ax-craziest blood knight ever to don pauldrons) was once Angron's more even-tempered advisor.
*** Of course, despite being the most berserk of all Berserkers ever, he's [[MemeticMutation a really great guy]]. That, or everyone's so terrified they won't even acknowledge to themselves how terrifying he is.
** Recent lore implies that, at one point, Kharn had the chance to walk away from all of it. A Loyalist Thousand Sons sorceror saw his pain and offered to remove the device that was driving him to rage. Kharn briefly realized what this meant and had considered it, but in a violent psychotic rage butchered the Sorceror. The Sorceror knew he would not survive Kharn's attack, so instead mentally related to Kharn exactly what his actions meant; Kharn can no longer blame anyone else for his pain and rage, he had the chance to cure it and chose otherwise. It's implied that this revelation broke what was left of Kharn's mind, resulting in the ruthless berserker the galaxy now knows.
* Moving away from individuals, the '''Iron Warriors''' spent the entire Great Crusade being brutalised by sieges and trench warfare. Now, after the Heresy, they've gone completely nuts and turn every single planet they live on into a super-reinforced stronghold ringed with all sorts of tanks, Dreadnoughts (which are batshit crazy, by the way) and Havocs. Relentless, merciless, and ''willing'' to infect themselves with the Obliterator virus (see below).
** One such example of what they're capable of is known as the Iron Cage Incident. They set up base on Sebastus IV containing a keep within 20 square miles of minefields, towers, tank traps, trenches, bunkers and redoubts in order to trap their opposite numbers, the Imperial Fists. The plan starts by isolating the enemy from their orbital support, all the while dividing them up to destroy them one by one. Finally, when the remaining Imperial Fists penetrate the fortress, there's no keep--just DeathInAllDirections. By day six, the Imperial Fists are reduced to fighting individually and using the corpses of their brethren as cover. The siege continues for three weeks after that. The end result is that the Fists' primarch is left a broken man, the Fists themselves are left unable to fight for nineteen years, and Perturabo (the Iron Warriors' primarch) sacrifices the geneseeds of the fallen enemy to ascend to the status of Daemon Prince.
* '''NightLords''' get their giggles from psychologically torturing entire planets. One piece of fiction has them crucifying and eviscerating loyal Assault Marines, then nailing the iron crosses to the front of their tanks. ''And the Assault Marines were still alive''.
** In another piece of fiction the Night Lords invaded a hive city (a planet covered in mile high cities) and hacked into the telecommunications networks and broadcast the murder, death and torture ''as it happened.'' The Imperium reports after the attack stated that fully one-third of the population died from ''fear itself.'' Total. Nervous. Shutdown.
*** Summed up well by [[http://1d4chan.org/wiki/File:Oh_shit_the_batmarines_by_sonicbrew-d2z88fe.jpg this image]].
*** Also, in the same book, they came up with a plan [[spoiler: to shut off all psychic communication and Warp navigation in an enormous area of Imperial space]]. How they achieved this? Flaying every astropath on the hive planet, ''keeping them alive for hours afterwards with medical treatments to prolong their agony'', and finally killing them by exposing them to Navigator Octavia's third eye, which released the build-up of psychic energy that their suffering had created. And the strain of that almost killed her as well.
** The Night Lords were nuts even before the Heresy. Failing to get enough recruits, the Primarch resorted to [[PsychoForHire using psychopathic criminals]]. True, he regrets it at the end and hated what the legion became, but one must remember: the Primarch himself was considered [[AxCrazy a homicidal psychopath]] before becoming Primarch, ''and he hated what the legion has become''. It's even suggested that he allowed himself to be killed by an Imperial assassin because he was so deeply and utterly horrified by what he himself had become. The entire legion basically runs on this trope.
*** He let himself be killed as vindication; he had been DreamingOfThingsToCome ever since he was a child, with one of the dreams being the exact circumstances of his death. He allowed the assassin into his chambers, watched her walk up, and flat out told her in only slightly more grandiose speech that "everything I have ever done is proven to be in the right by your presence here." This includes betrayal of the Imperium, and the [[EarthShatteringKaboom destruction of his own homeworld]]. And he's RIGHT. ''Yikes.''
** Said Primach, Conrad Kurze, was a combination of Franchise/{{Batman}}, ThePunisher, [[Film/ApocalypseNow Kurtz]], and {{Satan}}, as a demigod. His Chapter learned well.
*** [[ShoutOut Colonel Kurtz]] was, in fact, the admitted inspiration not only for his name, but several aspects of his character, including [[DyingMomentOfAwesome his speech to the Imperial assassin that killed him.]]
** Kurze's modus operandi was to be the worst person on his planet, so that no one else tried to claim the place. It worked. How did he do this? By killing EVERY single criminal in a brutal manner, until the planet's sewers were jammed by their body parts. [[CrapsackWorld This was still considered an improvement over his predecessors.]]
** [[BlatantLies Here's something to think about to help you sleep tonight]]: the Night Lords were originally depicted as extra-awful psychopaths back when Space Marines ''in general'' were often recruited from maximum security prisons. It was later changed that Space Marine indoctrination had to begin at an age of between 10-12, coinciding with the onset of puberty. The Night Lords are still, canonically, depicted as being gathered up from amongst groups of depraved murderers and maniacs, ''despite not being old enough to attend high school''.
* '''Word Bearers''' are the Imperial zealots with [[ReligionOfEvil all that fanaticism turned to the Dark Gods]]. And they're the ones who kicked off the HorusHeresy - in other words, the entire fucked up state of the 40K universe? Lorgar's fault. '''The entire hell-universe that would give Stephen King night terrors is Lorgar's fault'''. Even the ''Imperium's'' current state is Lorgar's fault, because he wrote the original Lectitio Divinitatus tract slash holy book.
** Backstory from the ''[[DawnOfWar Dark Crusade]]'' campaign included a pious individual named [[MeaningfulName Virgilius]], some Vlad the Impaler-style human sacrifice, and seven "volunteers". One of the sacrifices chickened out at the last minute, but luckily two of his companions were able to catch him and hoist him onto his pike anyway (in his screams he “issued the fifteenth curse,” which the temple presbyter took as a ''good omen''). Once everyone else was “[[DeadlyEuphemism positioned]],” the presbyter had one last concern that Virgilius would refuse to do what was required of him, but he needn’t have worried: Virgilius climbed onto his pike without a qualm, and then ''opened his abdomen with a consecrated knife and let his entrails fall to the floor.'' The reason for all this? The sacrifice of eight souls this way opened a portal to the Warp so that [[EnsembleDarkhorse Eliphas the Inheritor]] could start his campaign on Kronus. That’s right: ''just requesting military support from the Word Bearers involves ritual murder-suicide.'' It might not be canon, but holy shit it’s illustrative.
* '''Emperor's Children''' Pray to the emperor that you never meet these guys. These sick bastards will rape you, your family, and then liquify you all down into combat drugs. And they will most likely stitch open your eyes and ears beforehand, so you can experience it all in mind-blistering detail. Why? 'Cos it's fun.
* '''Black Legion''' are the apex of this. Because they are ''all of the above''. The rampaging Khornate psychopaths? They have those. The sadistic Slaaneshi cultists? They have those. The silent, decaying monsters that look like zombies in power armour? They have those. They have access to every single horror in the Chaos list and then some.
** And their boss? Abaddon. The BigBad of the entire setting. He is a massively powerful, terrifying being of infinite malice and cruelty. He alone, of all Chaos Space Marines, can bring all sides together for his Black Crusades. All four Chaos Gods have agreed that he and he alone is worthy of leading their forces in the absence/disinterest of the Primarchs. He's never won, but not due to his own weakness. It's because the Imperium has EVERY POSSIBLE ADVANTAGE IN FIGHTING HIM. He commands tens of thousands, maybe a hundred or so thousand total Chaos Marines, and maybe a few million other guys, tops. The Imperium has over a MILLION Space Marines, and literally TRILLIONS, i.e. MILLIONS OF MILLIONS of other dudes. The Imperium also has way more ships and war machines, and the advantage of being totally, one hundred percent united against Abaddon, who is barely able to hold his own forces together. Not because he isn't awesome. Because the only people Chaos hates more than the Imperium are the rest of Chaos. ''And the Imperium only '''barely''' wins.''
*** He has his own mark of chaos. The only others who have Chaos marks are ''the gods.''
*** Abaddon is also a good candidate for FridgeHorror style HONF. Chaos is ''not'' forgiving of failure, with typical punishments ranging [[YouHaveFailedMe getting killed by your superiors]] (and even if you live or evade this, your "allies" and "loyal troops" will start seeking to kill you and take your place) to your patron god [[BalefulPolymorph warping you]] into the [[BodyHorror screaming, mewling, heaving mass of unsane flesh and bone]] known as a [[AndIMustScream Chaos Spawn]]. Abaddon, despite his many failures, doesn't have any such problems facing him, and thinking about just why this is, when he's under the gaze of ''all four Chaos Gods at once'', is certain to raise "OhCrap" possibilities.
*** A common misconception among fandom is to depict every Black Crusade as an attempt to march to Terra that was stalled at the very beginning on Cadia due to Abaddon incompetence. While in fact, most of the [[http://images4.wikia.nocookie.net/__cb20130831031104/warhammer40k/images/e/ea/BlackCrusades3.jpg Black Crusades]] slipped past Cadia and went for their objectives with little difficulty. It should be noted that most Black Crusades were not an all out assault against the Imperium, but rather quite a limited operation with a certain goal in mind. The only Black Crusade that was stalled at Cadia for some time was the 13th one. [[note]]The manner GW handles updates makes strong impression that Abaddon tries and fails to capture one little planet for 20 straight years getting beaten over and over, since the first Eye of Terror codex was published. In in-universe terms the 13th Black Crusade has just started. The timeline ends at the very start of the 13th Black Crusade and it will remain unresolved until GW decides to move the plot along. Which is most likely never.[[/note]] Almost all the Black Crusades were launched to achieve a certain, very limited goal. Be it the powerful artefact, intel, resources, slaves, tech specs, wipe of some Space Marines Chapter, ancient Death Star battlestations, Abaddon will get it, ditch the his allies and fall back to Eye of Terror with his Black Legion troops. The incoming reinforcements of Imperium crush the disorganized rabble of Chaos warbands and report about their glorious victory over the Warmaster's forces. Yet Black Legion suffers next to no losses, gains tonns of resources and manpower to build more ships and war machines, while the value (and danger for the Imperium) of the fully activated Blackstone Fortresses or the [[ExactlyWhatItSaysOnTheTin Planetkiller]] simply cannot be measured.
* '''Alpha Legion''' are about the only ones with [[NecessarilyEvil a sympathetic motive]] that they may or may not have lost over the past ten millennia (currently their modus operandi tends to be about enforcing a particularly brutal brand of LawfulEvil). However, nobody really knows their motives, their leadership, or really anything about them at all. Their Primarch, Alpharius, was the youngest and last discovered, [[TheUnfavourite more or less ignored by the others]] (except Horus) and as it turns out, may have a twin brother, [[ThemeNaming Omegon]]. Alpharius may be dead; nobody's sure, because it wouldn't slow them down. The Alpha Legion's mascot is the Hydra, and their motto is "Cut off one head, two more replace it."
** The really scary thing is that it's very strongly hinted that the Core of the Alpha Legion at least, is well and truly loyal to the Emperor despite their Daemon usage, chaos cultist cannon fodder, fondness of spikes, and the occasional warband that has lost sight of their goal and truly has fallen (Like Lord Bale's or Fieravious Carron's). Everything they do, they do for the Emperor.
** As it turns out, their motive itself reveals some added horror--it was revealed to Alpharius that if Horus were successful, humanity would be wiped out within two generations, but Chaos would ultimately be broken. If the Emperor won, however, he would be trapped within his own body on a golden throne, and humanity would stagnate and decay over the course of the next 10-20 millennia, enabling Chaos to overrun the entire universe. [[DoomedByCanon Welp.]]
** As explained further down, destroying Chaos is difficult, if not impossible. So the Alpha Legion have a goal based solely on InsaneTrollLogic: Chaos must be defeated so save humanity. Chaos is powered by humanity's existance. So the easiest way to destroy Chaos is to kill all humans, thus Chaos will become powerless and humanity is sav... '''wait, what!?'''
* You know what's really freaky? So many named characters of the Chaos Space Marines were around during the Horus Heresy. Which means the Emperor built his Empire with these psychopaths, many of whom willingly sold themselves to Chaos. [[GoodIsDumb The Emperor, humanity's greatest hope and salvation, was an incredibly]] HorribleJudgeOfCharacter.
** Another, not exactly more reassuring, theory is that he was, in fact an incredibly good judge of character (of course, character seems to have had little to do with it, considering they were created to lead, not raised to). He surrounded himself with humanity's best and brightest. And it still wasn't good enough.
*** The problem isn't really that they were not good enough, the problem is, that they are actually the best. Think for a moment about the prospect of what chaos actually is. It's a warp of whatever happens to be, as described a few paragraphs up and if what was revealed to Alpharius and Omegon is even only remotely close to the truth (and not another trick and treat by Tzeentch) and the happenings within this world pretty much back this claim up, then your only way of getting rid of chaos is, to simply not exist at all. As long as people are fighting for their life, there will be Khorne. As long as people want a better life, there will be Slaanesh. As long as people lay out plans to do things, there will be Tzeentch. As long as there is creation, there is Malal. As long as really anything is alive, there will be Nurgle. The harder you fight, the more you wish for a better tomorrow, the more you cling to your very survival, the more walls you raise to defend you, the more elaborate your plan on how to achieve all of this is, the more powerful Chaos becomes and by ever increaseing your effort, you work in exactly the wrong direction and so it happened with the Primarchs.
* And on another Chaos note, '''Obliterators'''. Basically, think of a Chaos Space Marine combined with a Dreadnought. These guys are Chaos Marines infected with a virus from the Warp (so essentially a virus that haunts the nightmares of other viruses) so that it morphs their bodies, melding them with their armour, turning them into piles of flesh and metal, and allowing them to absorb artillery weapons into their bodies and spontaneously spawn ammunition for any weapon. Couple that with the fact that they're all gibbering lunatics from being in the Warp for so long...
** They were originally Traitor Legion's Techmarines (so, some bionics already), but years in the warp and "blessings" by the dark gods caused the Obliterator virus to appear. Someone actually wrote an account of a Techmarine slowly turning into the monstrosity that is an Obliterator - in very slow and agonising detail. For example - Techmarines have various plugs and sockets in their flesh (mainly hands and head - that they feel all the time) so they can 'communicate' with machines - well, the virus caused the weapons to spawn from these. Very small holes, the size of a coin - having HUGE anti-tank missile launchers, or heavy machine guns, several times the size of the plugs, being pushed out. Veeery slowly....
* Think Obliterators are bad? They've got a close combat equivalent now, called Mutilators. Imagine the same nightmarish shifting morass of flesh and metal... and have it instead be fixated on melee combat, constantly reshaping itself into newer implements to slash, stab, skewer, maul, mangle, and mutilate. Worse, Mutilators ''chose'' this state; they deliberately hunt down "weapon spirits" in the Warp and devour them, absorbing them into their bodies to become what they are now. So, in comparison to Obliterators, Mutilators are technically sane...
* Raptors are what became of Assault Marines; they're particularly associated with the Night Legion. And they get worse, too; Raptors eventually devolve into Warp Talons, monsters that live only to hunt... and how do they hunt? They use their {{Absurdly Sharp Blade}}s to ''cut portals into the Warp so they can fly through Hell and pop out anywhere they sense battle''.
** That's not even the worse of it, Warp Talons are usually hired to assassinate certain key enemies, how do they find them? The employer gives them an item precious to the target a locket, a watch, their old favorite toy, [[BreadEggsMilkSquick their mother's index finger]], and the Hell Talons use that to teleport directly to their target. In other words, it doesn't matter where you run, where you hide, the Hell Talons will literally tear through another dimension to get to you...
* Heldrakes, Forgefiends and Mauler Fiends.
** The Heldrake used to be a space marine aircraft, but over time the pilot literally (And very slowy) starts to become one with the vehicle, they start seeing with the ships sensors, they speak with the vox. Eventually they are reduced to nothing more than a battery for the machine, forced to an eternity with only the mad daemons they will forever be room mates with.
** Forge fiends have potentially limitless ammo, that doesn't sound too bad right? However the means in which they create the ammo is the horrifying part. The Forgefiends literally devour anything on the battlefield, from metal to corpses, in order to gain resources for their mechanical intestines to use to create more warp powered shells.
** The most horrifying part about the daemon engines is their very creation, the Warp Smith's (The one who creates the monsters in the first place) chant about it sums it up. "Shackle the soul and forge the flesh. Bind the machine and butcher the rest."
* Chaos gods, worshipers, cultists, demons, vehicles etc all spread absolute fear and terror and are the stuff of nightmares. So then why should their very homes be any different? Each of the four Chaos gods resides in their own domain within the Warp whose landscape defines their characteristics. My favorite little nightmare lair is Tzeentch's Maze. The Maze has no defenders but does that mean you're safe? Oh hell no. It is basically a giant swirling ever-changing maze where the laws of physics, gravity, reality or ANYTHING are virtually non-existent. Should you be stupid enough to somehow wander into the Maze of Tzeentch, expect to find yourself lost on your very first step and watch the path you took suddenly disappear forever. Then as you wander aimlessly in the ever-changing maze, which can include colors and objects that doesn't even exist in the universe, you will slowly and surely be driven into complete madness and despair and you soon die of insanity. Oh and since the Maze is within the Warp, when you do die your soul is gonna remain there so there's no escape from it even in death.
** Khorne's realm is basically Valhalla on steroids; he sits on a throne of brass atop a mountain of skulls, which grows with every death in combat. His chamber is lit by dark flames which consume the souls of deserters; warriors who died in their sleep are forced to man his war machines for eternity. His citadel is surrounded by a moat of blood, and features a battalion of Orks in a constant state of war, constantly resurrected to fight. The Orks, however, [[ValuesDissonance think they've found paradise.]]
** Nurgle's realm is a garden of every hideous form life; it swarms with flies and rot and is chocked with poisonous thorns and crossed by sloshing mires. Great groves of giant fungi and wilted leaves form the bulk of the scenery.

* The '''DarkMechanicus''' full stop. Every little crazed Mad Scientist trope that comes to mind? The Dark Mechanicum are this and oh so much worse as they combine their knowledge of technology with Chaos and even occasionally Xenos devices. But that's not the worst part. Some of it's members are literal nightmare fuel too.[[/folder]]

!Xeno Races

[[folder:'''Tyranids''']]
* '''[[HordeOfAlienLocusts Tyranids]]'''. Like Giger's Franchise/{{Alien}}s, but [[UpToEleven smarter and meaner]]. They come in an ever-growing range of sizes and shapes, from human-sized monsters to living HumongousMecha, all [[BioAugmentation deliberately evolved]] towards a single purpose. They have [[BreathWeapon biological ranged weapons that spray acid and venom]] or [[BeeBeeGun fire swarms of flesh-eating maggots]] [[DoesThisRemindYouOfAnything via muscle spasms]]. When they attack your world, they [[AlienAmongUs send vanguard organisms to corrupt your genes]], resulting in a cult of {{h|alfHumanHybrid}}ybrids that psychically summons the hive fleet. Note that these vanguard organisms themselves are terrifying creatures that exceed the human potential of speed, dexterity, strength, [[strike:constitution, intelligence, wisdom, charisma, AC, hit points, base attack bonus,]] resilience, and sheer terror so many times over that these are often enough to cause widespread genocide in and of themselves. Once the hive fleet arrives, they seed your atmosphere with spores that drive plant life into a growing frenzy, [[ZergRush then they rain down swarm... after swarm... after swarm of chittering monsters]]. These range from [[WeHaveReserves uncountable numbers]] of lowly Gaunts, who are cannon fodder which is more than capable of disemboweling you, to Carnifexes, which [[GiantMook rival a tank in firepower and toughness]], to the lumbering Bio-Titans, which make Franchise/{{Godzilla}} look like a pet iguana - a nice iguana, at that. The HiveMind of the species disrupts space travel and psychic communication, so there's no way to call for help and no way for it to arrive, and no way for the tasty little bioforms to escape. Once they've overrun whatever pathetic resistance you attempt, they send down speciality creatures to eat ''{{e|xtremeOmnivore}}verything'' on your planet - plants, animals, even their own troops. The fleet sends down feeder tendrils to slurp up this digested bio-fuel and siphon the very water and atmosphere off of your world, leaving it a [[ApocalypseHow lifeless rock]]. After consuming ''everything'', [[AdaptiveAbility they instinctively scan the DNA of the creatures they've devoured for useful evolutions they use to upgrade the swarms]], before moving on to the next world. Oh, and they outnumber the stars.
* There are two throwaway pieces of background in the current Tyranid Codex (i.e. rulebook) that are particularly horrifying:
** No.1: During the first ever human encounter with the Tyranid race, they hit a mining world. It basically turns into ''Film/TheDescent'' [[InSpace IN SPACE]] with vast hordes of terrifying alien monstrosities. ''Alien 3'' done right.
** No.2: A little later in the timeline, a ship full of refugees from a world under attack from the Tyranids turns up at its destination, drifting lifelessly in space and not responding to any attempts to communicate. When the Imperium investigates, they find that every. Single. Person. On the ship has been brutally slaughtered. But there is no sign whatsoever of the thing that did this.
* ''"Warn them, warn them! The Tyranids are coming! THE TYRANIDS ARE COMING!''"
** ''"They are coming! I feel them scratching inside my mind, scratching, screaming, running, so many - so, so many voices. They're coming for us - flesh, body and soul!"''
* The '''Lictor''' is custom made for this trope. Over two metres in height, possessing both [[SinisterScythe massive scythes]] for tearing apart tanks and [[CombatTentacles delicate tendrils]] for [[BrainFood eating brains]] (from which it [[GeneticMemory absorbs the victim's knowledge]]), it is so ridiculously agile and stealthy its targets are often not even aware of its presense until after they find themselves severed at the torso, and it is not uncommon for their skin to be {{chameleonic|Camouflage}} to further aid in infiltration. It also has a tendency to exude chemical signals to draw other Tyranids to its location with the amount produced directly related to the size of resistance, so even if you do manage to kill it you then have to deal with the rest of its friends.
** Deathleaper, a special Lictor, takes this slightly further. Suffice to say, something which can go back into hiding quicker than your troops can react AND has been tormenting a character in your army for a long time isn't fun to fight the first time...
*** The fluff about Deathleaper is even worse. The first recorded occurrence of the creature was on a heavily fortified Imperial shrine world that the Hive Mind decided was too strong to take in a head-on attack. It installed Deathleaper there and told it to find the leader of the planet and assassinate him. After stalking for a while, Deathleaper found the governor of the planet and attempted to kill him, but was repulsed by his bodyguards. So it began a campaign of psychological terror - every day it would infiltrate the governor's palace, butcher its way to the governor but then leave him unharmed. The governor had to deal with the loss of his advisers, scientists, commanders, friends, bodyguards and family, until it got to the point where Deathleaper entered the room the governor was residing in, killed everyone inside except for his target, and left him sniveling on the ground, coated in the viscera of his friends and allies. He took his own life minutes after this attack, leaving the defences of the planet thrown into disarray. The Hive Fleet consumed the world within the end of the week. Be glad the psychological warfare rule he has only deducts d3 LD from an enemy character...
* The Imperium has currently encountered three major Tyranid Hive Fleets: Behemoth, which had over a thousand hive ships and countless other smaller ships and Emperor knows how many ground organisms, which killed the entire Ultramarines first company and almost devoured Ultramar; Kraken, which was much, much bigger than Behemoth (Behemoth was only ''30-40%'' the size of Kraken), was the first to develop genestealers (the aforementioned hybrids), and nearly destroyed the Iyanden Craftworld and the planet Ichar IV with tendrils that were themselves as big as the whole of Hive Fleet Behemoth, if not bigger; and Leviathan, which is all-surpassingly gigantic (from a picture in the 5th edition codex, its main mass of tendrils is ''a third as wide as the milky way galaxy itself'' - that's ''50,000 light years of hive ships''), which has only been slowed by initiating {{E|arthShatteringKaboom}}xterminatus on any planet they infect. All of them have only been [[PyrrhicVictory repelled with massive losses]] and none of them have been defeated, each producing numerous splinter fleets; though the main body of Kraken and Behemoth have been destroyed, there seems to be no end to the number of tendrils constantly coming upwards at the Galaxy from Leviathan.
** Do you want to know what's truly horrifying about all of this? [[spoiler: Kraken, Behemoth, and ''Leviathan'' were just ''scouting divisions'' designed for reconnaissance, not actual invasion. The ''actual'' invasion fleet, based on the little evidence we are given, is anywhere between ''50 to 500 times larger than Leviathan''.]]
** A nitpick, if I may: Genestealers were first encountered well before Behemoth's incursion; they were previously believed to be a predator native to the moons of Ymgarl. This was literally an OhCrap moment for the Imperium; Genestealers were employed by Behemoth as shock troops, and confirmed by Imperial techno-magi to be Tyranid creatures. So what, exactly, are they doing all over the galaxy, and why do they seem to have been here for a really long time?...
** More specific details: the Ultramarines First Company was composed entirely of ''veteran Terminators.'' They had a well-fortified position, and enough ammunition and supplies for months of continuous siege, yet they ''still almost ran out of ammo.'' They killed ''millions,'' enough that the ground wasn't visible under all the corpses. And one of the early worlds that was overrun had all of its anti-air guns found bone-dry of ammunition. The Tyranids simply had more bodies than the defenders had bullets.
* And then there's the fact that it's heavily hinted that this is at least the Tyranid's ''second'' go through this galaxy, i.e. they passed through our galaxy millions or billions of years ago and wiped out everything (bar the occasional Ymargl Genestealer) so throughly that ''there were no records of them whatsoever''.
* The Hive Tyrants themselves can be upgraded to have a rule that weaponizes this trope: Indescribable Terror. Aside from a few Fearless individuals, this would make even Space Marines crap their pants in horror and refuse to attack.
** Certain Tyranid Synapse creatures also have a rule called "Shadow in the Warp". Essentially, this is the psyker's version of Indescribable Terror, only that it can literally tear your head apart.
** The terrifying part about Shadow in the Warp is that it's literally ''nothing''. It's basically space static. ''And it's unnerving''. The tyranids managed to weaponize NothingIsScarier and use it to devastating effect against other psykers.
* One must wonder if some of the new [[GameBreaker game-breakingly powerful]] specialised Tyranid breeds are. Subject One - the Doom of Malan'tai. In its fluff, it destroyed an entire craftworld by literally eating the souls of the dead from the Infinity Circuit. Now just stop and freeze frame a second. There's no sign of the creature, but who's to say it hasn't found a way off? Who's to say all the souls it's eaten didn't give it protection from the vaccum of space? Who's to say that [[ParanoiaFuel a bad codex writer didn't just put the God Emperor in the form of a Tyranid? Who knows how many souls it's eaten since, and how much power it now has?]]
** Another less powerful but still nasty fleet was Hive Fleet Naga, whose accomplishments include the devouring of four outer colonies and the Throneworld of the Ulumeathic League, the wiping out of the Ybaric Cluster, and the destruction of two Eldar Maiden Worlds and seven Exodite Worlds, including by crippling the world spirits of several Exodite worlds by the devouring of a single Exodite world. Also, they created the Doom of Malan'tai.
* The Venomthrope is covered in tentacles and sprays venom, spore clouds, and all sorts of assorted toxic monstrosities at its enemies. Trygons and Mawlocks are huge snake-like monsters that can burst up from any point of the ground whenever they please. These are just some of the lovely things you can find in the 5th edition codex...
* The battle of Sondheim V. A peaceful Agri-world in the Imperium of Man that has been up to that point far removed from any conflict for thousands of years suddenly sees the skies turn into a multihued mess as the Daemon prince M'kar the Reborn decides to turn it into his private playhouse and Daemons start running loose everywhere. But soon after this a tendril of Hive Fleet Leviathan descends upon the planet and the sky starts glowing in other weird colors as endless numbers of Mycenic spores rain down upon the planet. Gaunts, Genestealers, and Warriors start fighting Bloodletters, Horrors, Daemonettes and Plaguebearers, utterly undeterred by their Daemonic nature. Gargoyles and Furies gnash and tear at one another in the skies while Carnifexes, Tyrannofexes, Hive Tyrants, and all sorts of bio-titans fight Greater Daemons in the streets. Nurglings and Rippers devour one another while Zoanthropes fight psychically with Lords of Change. Now this may sound awesome, but imagine if you were just a normal Imperial Citizen cowering under his bed while watching two of the greatest horrors in the Galaxy have a go at each other. The entire Sky Sentinels chapter is sent to reclaim the planet, but the whole thing is so terrifying that they just decide to Exterminatus the place and blow up the hive fleet tendril.
* The Shadow in the Warp. The mass of Tyranids in the hive fleet is so incredibly huge, the subconscious buzz of all their minds adds up to ''[[BeyondTheImpossible drown out the Warp.]]'' This renders all FTL travel and communications impossible, and presumably also makes Daemons shit themselves.
* And now for FridgeHorror. The Tyranids are so psychically powerful and so ''interchangeable'' that they function, basically, as a single absolutely ''enormous'' organism. It's like a termite colony fifty billion light years wide. For the Tyranids, going into the Milky Way and fighting off the most {{badass}}, [[SuperSoldier overpowered]], terrifying, [[PhysicalGod divine]], [[WallOfWeapons well-armed]], [[PatrioticFervor devoted]] warriors in the galaxy is probably just like getting a mild case of food poisoning from a tasty leg of chicken.
** And, as if it wasn't bad enough that there's a swarm of interstellar locusts the size of the galaxy descending on us, an increasing number of hints and inferences point to the fact that there's something ''drawing'' the Tyranids in: the Astronomican. You know, the giant beacon of psychic light, powered by the Emperor's immeasurable energies (and the souls of thousands of psykers a month) that is the only thing that lets mankind travel the Warp with any sense of direction at all? To the Tyranids, that thing's one great big neon "FREE BUFFET" sign.
* Then, there's the fact that Imperial tacticians are utterly confused about how in the blazes massive Tyranid forces are popping up all over the galaxy, often too closely together in time to account for what FTL speed they have. Then someone had the mother of all OhCrap moments: they'd been plotting everything out on, essentially, a 2D map of the galaxy, assuming they were coming in from the edge. The Tyranid fleet was ''coming up from beneath.'' [[Film/{{Jaws}} Dunnnn dun...]]
* And there are the hints. Just hints, nothing concrete. There are hints, now and then, of something very, very unpleasant. The Tyranids aren't really ''invading'', these hints say. ''They're fleeing.''
** If the Tyranid galaxy is in some ways parallel to the Milky Way, and perhaps one that didn't have as many Dark Ages, maybe they're that galaxy's '''good end'''? With civilization(s) reaching biotech as the ''apex'' of technology, mastering the Warp with psychic gestalt-entities, developing reliable means of FTL travel, capable of fantastic terraforming, and beyond; they could settle down, but instead they eat & run. [[AlwaysABiggerFish What's so bad that they would flee their entire galaxy to escape it?]]
** More to the point, what could possibly be so horrifying that they would flee to ''this setting'' to escape it?
* Another less known theory, is that the Tyranids and their Hive Mind are either the creation of, or the Old Ones themselves, returned. There's a subtle hint in the 5th edition Tyranid codex, where one of the race's pseudonyms is "the Penance of the Old Gods". Think about it. The Old Ones were an all-powerful race of immortal, psychic demigods who ruled the Milky Way galaxy eons before the rise of the other races. They created the Eldar and the Krork (the Ork's precursors) as weapons to help fight against the Necrontyr and their C'tan masters during the War in Heaven. After they lost the fight to the C'tan, and the emergence of the Enslaver Plague, they simply disappeared. Nowhere is it specifically stated that they went extinct, more like that they abandoned the galaxy.And nowhere does it state that they were a benevolent race. This being 40k, one could argue that they dabbled in creating new life forms irrespective of the danger they might pose. Both the Eldar and the Orks are flawed creations, made flesh simply as a last ditched effort in spawning weapons capable of using the tremendous nascent forces of the Warp in order to defeat the C'tan. The Eldar's flaw being that despite their wisdom and mastery over psychic power, they were creatures slaved more to their emotion than to their intellect and reason. And we all know what this lead to...while the Orks have even MORE psychic potential than the Eldar, but not even a fraction of their control over it, yet they are the most successful survivors in the galaxy. So the Elder Ones definitely have the power to create new lifeforms, and are beings who operate on cold-blooded logic and reason, with the power to shape worlds and races. If they reason they could create another survivor race of warrior creatures with complete immunity to Warp corruption, in order to wipe the Milky Way galaxy of life so the C'tan and the Chaos Gods would be starved of sustenance and they could return to a wiped slate to start over, there is no reason why they wouldn't just go for it. In short, the Tyranids could be either another of the Old Ones' creations (under their direct control -- or successful rebels who finally wiped them out) or the Old Ones themselves, voluntarily mutated into an apex superorganism -- the pinnacle of evolution, returned with a vengeance to "fix" their past mistakes by assimilating every living thing in the galaxy.
* No love for the Swarmlord? The thing is the oldest and most ultimate weapon of the Tyranid species, used only in desperate situations where a hive's normal tactics fail, making it capable of transferring between hive fleets just because it's THAT old. The Swarmlord's mere presence is able to turn the tide of battle for the hive fleet it joins. This thing is the '''SMARTEST TYRANID EVER MET''', meaning that this thing can out-think practically anything it meets and capable of acting independently from the HiveMind. It also has four specialized boneswords which it uses at such blinding speed that it can effectively parry every single move you make without fail, and then use it to tear through any armor you put up like tissue paper. And if you get lucky and kill it? It'll just come back, just as deadly, knowing everything that just happened before you killed it and ready to enact hideous revenge!
** Face it. What makes the Swarmlord so scary is not that it's an enormous psychic abomination capable of shredding tank armour to ribbons, or that it's a highly intelligent individual in a species defined by being mindless warrior-drones of varying sizes. It's the fact that it's basically the Tyranid [[http://1d4chan.org/images/6/68/Tacticalgenius.png Ursarkar E. Creed]].
* Genestealers are scary-looking enough when they are purestrain but as they become more and more hybridised they become even creepier as they take on human traits and eventually become a perfect hybrid of unfeeling alien and charismatic human. And then you consider how they breed as revealed in the novel Deathwatch by Steve Parker. Genestealers need to get human genes from somewhere, so they have their cultists abduct women and then get new Genestealers through two methods. If they want purestrains then an already existing purestrain uses it's tongue to infect the woman with a genetic packet of Tyranid DNA that will cause a brood of genestealers to grow in them. After a horrifically painful pregnancy, all the while they are sealed in the Genestealer hive and fed nutrients through bio-tubes that go into their mouth, stomach and possibly ''other lower places'', the baby Genestealers tear their way out of the women, exactly where they tear their way out of isn't specified, and devour every last scrap of their mother. But if they want hybrids, it may actually be worse. They hypnotise the women into submission and have their hybrids rape them, impregnating them with future generations of Genestealers that will appear to be normal children who will hold their mother in complete thralldom and use them to breed more and more generations until finally they die.
** Of course, the standard Genestealer isn't a cakewalk either. They don't have any ranged weaponry, but they strike from the shadows with sharp claws. How sharp? An Adeptus Astartes in full-on Terminator armor is nothing but a walking minced tuna can to one of these things if they catch them off-guard.
* Because of the combined nature of the Tyranid's Hive Mind and Shadow in the Warp, they are one of the few races in the galaxy (alongside the Necrons and Tau) that Chaos absolutely cannot touch. Think about that for a second...
* There's also the utter Alien-ness of the Tyranids; all of the other races in the game can have their origins tied to another faction, and ultimately to Chaos and the War in the Heavens. The Tyranids are ''completely out of context'' from everything else. They're a constant reminder that no matter how crappy the galaxy can get, all of the conflicts are a drop in the bucket the moment you step out of the eastern fringe.
[[/folder]]

[[folder:'''Eldar''']]
* The '''Eldar''', creepy beautiful aliens in thrall to the god of lust, which they created by accident after their galaxy-spanning empire became too hedonistic. Fortunately, most of the survivors are [[DefectorFromDecadence really sorry about it and have learned their lesson]], so they only kill people when it becomes necessary, as opposed to when it becomes fun. However, they also ritualistically cultivate [[SplitPersonality multiple personality disorder]] of a sort to keep from being traumatized in battle, so when they go to war, they're so driven by cold rage and bloodlust that they seem on the brink of sanity. They also use very, very nasty weapons. I say "most" because there's the creepier versions that are still all about the murder-orgies and largely consider the destruction of their empire and 99% of their species a slight inconvenience in that they now have to hide in a pocket dimension to get away from the thirsting maw of the god they created.
** While we're on the topic of cultivating multiple personalities, Exarchs have dropped this and don't care about anything other than their aspect of war. So they tend to their shrines, dedicated to training their warriors and [[BloodKnight nothing but combat]]. They've effectively made it so that they've completely lost their old personalities (and whatever they liked doing, sculpting, cooking, whatever) and only want to kill stuff. Or perfect combat. They're also willing ritualistic sacrifices for the [[PhysicalGod Avatar]] thus becoming the Young King/Queen, which is done by walking into a literal furnace of holy fire (after having bloody runes of Aspect warriors carved into their skin and given a cup filled to the brim of their own blood.) What happens afterward isn't [[FateWorseThanDeath detailed explicitly]], but after that they have effectively become one with the Avatar and exist only to kill.
** Becoming an Exarch means merging your mind with those who came before you whose souls have fused into the armor. Normally this simply means you can commune with them and learn of their experiences. The tragedy is that since all exarchs are destined to join in their particular suit, you won't ever see any of your friends ever again (as they will join the infinity circuit instead). What's horrifying are those chosen to resurrect the Phoenix Lords; Phoenix Lords are the progenitors of their Aspect, and their Exarch suits are impossibly old. Because of their sheer will, a Phoenix Lord's personality will completely dominate that of its current wearer, which is how the Phoenix Lord reincarnates. This effectively destroys the wearer as an individual, his memories only useful to the Phoenix Lord as a warning against any recent dangers.
* The Eldar can A. [[DreamingOfThingsToCome see into the future]] and B. [[FantasticRacism place no value on the lives of other species]]. This means that if the only way to prevent the death of a single Eldar is to turn [[ApocalypseHow an entire world of humans into molten slag]], they won't even hesitate to do it.
* Also, think about Slaanesh's origin story very carefully: the Eldar actually {{SQUICK}}-ORGIED A GOD INTO EXISTENCE. That's fairly frightening itself... though [[FetishFuel perhaps a bit kinky]], too...
** Pretty {{Badass}} of them too.
*** [[FridgeHorror Read again: The only thing that could create a chaos god of fun, love, pleasure, hedonism etc. was an empire of sadomaso hedonists!]]
* The monofilament guns the Eldar use, the quite fittingly named [[NamesToRunAwayFromReallyFast deathspinners]], the ones that shoot several [[RazorFloss tiny monomolecular-edged cords]] through the target and then whip around really fast, turning the insides of the target into shredded organ goo.
** Naturally, it gets worse. The Biel-Tan craftworld have developed the Void Spinner, an artillery weapon which fires a cloud of the aforementioned monofilament wire onto the enemy, combined with a barrage of bacteria and wraithbone parasites that scours all life from the target area as they are killed by the slicing threads and are broken down on a molecular level, with everything from flesh to bones and rock and metal becoming nothing but goo. It was developed exclusively to remove all presence of the filthy lower races who dare to taint the world the Biel-Tan are reclaiming.
*** Though they mostly just use them against Orks which is actually a pretty smart tactic because it ensures more orcs wont be spored from the dead.
* Warp Spiders. They are able to teleport in and out of the Warp to evade danger. The bad part? Whenever they teleport, they stand a very good chance of NOT REAPPEARING, caught in the Warp by anything that is there. For this reason, they are regarded with equal parts fear, respect, and bewilderment.
* Also, [[UncannyValley they are not really that beautiful to humans]]. Consider that they're about 7-plus feet tall on average, with a build so slim that the human equivalent would be considered malnourished or anorexic. Then there's the fact that they move so quickly that normal humans to them seem to be moving in slow motion. Add on the general disdain for other races (disdain if you're lucky, genocidal hatred if you're not), the natural affinity for psychic powers, and you basically have TheFairFolk with monomolecular blades and RazorFloss guns.
** Earlier fluff has the Eldar as gaunt, ugly and weird looking, usually - the later and more recent stuff paints them as almost akin to Tolkien Elves. Looks like a case of DependingOnTheAuthor.
* And while we're on the note of the Eldar, the '''Harlequins''' are the folks that even the Dark Eldar don't mess with. They're [[MonsterClown circus performers in colourful armour]] who put on amazing, psychically-enhanced theatre of the legends and history of the Eldar race, and in battle they have weapons that are [[ThereIsNoKillLikeOverkill brutal even by the setting's standards]], such as a razor wire that liquifies your insides (called the "Harlequin's Kiss). The weird thing is that as guardians of the Black Library and foes of Chaos, they're relatively ''good guys'' [[BlackAndGrayMorality by Warhammer standards]].
** Their rictus masks and holosuits are grotesque, constantly shimmering and in motion, garish and baroque to many extremes. Death Jesters are another example, and in addition to wielding heavy weapons they can load their aptly-named [[NamesToRunAwayFromReallyFast Shrieker Cannons]] with viral shuriken ammo that causes enemies to [[{{Gorn}} explode into many pieces]], showering their allies with gore. Oh, and [[BadAss Solitaires]] as well.
* Even killing an Eldar will not remove it from this plane--as long as its spirit stone remains intact, it can be "repurposed" to further the Eldar's ends--the spirit stone is implanted into wraithbone, whether in a wraithguard or wraithlord (the Eldar's answer to a Dreadnought) or in the core of their craftworld. A wraithguard/lord's soul experiences life as a dream.
** The end game of this is to gather enough souls to incarnate Ynnead, the Eldar God of the Dead and the Eldar's last, best hope to free them from Slaanesh. The only problem with this is that "enough" in this case means every single Eldar soul.
* Let's talk about spirit stones, shall we? Why do they need them? Well, they keep the soul of the wearer in stasis for them to be claimed by the living. They need to do this because if the soul is left to go to the Warp, Slaanesh is right there waiting for them. [[TakeOurWordForIt We're not explicitly told exactly what]] Slaanesh does to an Eldar soul if he gets his mitts on one, but consider that a) Eldar are scared to even ''refer to him by name'' b) the whole stoicism thing is in place to prevent attracting his attention and c) they are willing to [[TheChessmaster manipulate]] whole civilizations into slaughtering each other to save the lives of small handfuls of their own kind, and are also willing to mount {{Suicide Mission}}s to recover spirit stones rather than risk them being damaged. Whatever fate awaits a soul claimed by Slaanesh, if the living Eldar are ''so'' unbelievably desperate to avoid it, it must be '''unspeakably''' horrible.
[[/folder]]

[[folder:'''Dark Eldar''']]
* Relevant quote from ''Bleeding Chalice'', on human slaves to the '''Dark Eldar''' (the aforementioned creepier cousins of the Eldar):
-->'''Nisryus''': ''That's not a human soul... it's xenos. Someone... someone [[MindRape tore out their souls]] and [[DemonicPossession put something else in there]].''
* First of all, you know what we said about the Eldar being sorry about creating Slaanesh and learning their lesson? Well the Dark Eldar are the ones who '''didn't.'''
* On the subject of Dark Eldar: the Talos. A robotic mecha shaped like a scorpion that works by seizing victims on the battlefield, stuffing them inside itself, and torturing them to death, powered and motivated by their dying agonies.
* More Dark Eldar stuff include poisons designed to kill you from pure pain, weapons that shoot the ghosts of insane tortured slaves at you, guns designed to cripple not kill (cripple from pain as opposed to any actual physical damage, although that happens too) with shrapnel splinters, so they can take you alive, Eldar who delightfully dedicate their lives to torture and creating freakshow Dark Eldar 'grotesques' who are driven beyond even these torturer's ability to cause pain, just so they can be unleashed on enemies and worse.
* Worst of them are the [[DeadlyDoctor Haemunculi]]: Think [[ThoseWackyNazis Josef]] [[MadScientist Mengele and]] [[TortureTechnician co.]] - AS [[TheFairFolk DARK ELVES]] [[SpaceElves IN SPACE]]! They go into battle with ultrahorrible poisons (often disablingly painful but nonlethal) to get experimental material. [[BodyHorror And however they rearrange your anatomy]] ([[FateWorseThanDeath in at least one case including]] [[{{Squick}} YOUR ORGANS HANGING SEPARATELY AND ONLY CONNECTED BY VEINS AND NERVES]]), [[AndIMustScream you can't even pass out]].
* The Dark Eldar only care to obtain spoils of war, i.e. slaves, experimental subjects, etc. From their perspective, "DEATH IS A GIFT"!
* Well, the Dark Eldar do have at least one [[SubvertedTrope Pet The Dog]] moment, as shown in this comm recording of them offering amnesty to the residents of Section 9 which they put under siege. [[TooDumbToLive Maybe they aren't as evil as others let on]]:
--> "[[BlatantLies I am truly disappointed]] that the cruel fate has placed us in this position, such that I really have no choice other than to unleash my warriors against your population centers. If only you would lay aside these foolish hopes of protecting your resources and return to your homes and families, [[BlatantLies much bloodshed and woe could be avoided]]. Yet... there is still time, [[BlatantLies any who leave now will be spared and I give you my word that they will be granted free passage through the wastes.]] This offer of amnesty will stand for two of your hours before the terror begins anew. I can only hope that you consider your position carefully. [[SchmuckBait Send forth a representative to discuss further terms if you wish, or several if you cannot trust one of your number to speak for the rest.]] I feel sure that all can be... accommodated."
* Anything out of the new Dark Eldar Book is filled with this, from abilities gained from pain to having biological wings stuck on you and your bones hollowed out. However special mention goes to the Wracks and Grotesques, who are malformed, grotesque beasts made to be the servants and bodyguard of the haemonculus. The worst part? Wracks are made into these ''willingly''.
* And the reason they do all this? remember what we said about them being just like the Eldar that manifested Slaanesh? They only escaped the fates of the other Eldar because they were off partying in their own little pleasure-verses. Slaanesh very much wants to finish devouring their souls, and they can still feel his pull on them. Their only recourse is to replenish themselves with regular doses of the suffering of others, and hurl the souls of their victims to Slaanesh in their place.
* The new fluff states that they get an intense high off causing pain to other sentients. Given that they already have next to no self-control when it comes to their own pleasures and vices, but they actively go out and hurt as many people as possible. Given that they have the ability to resurrect themselves with their technology, battles that humans consider as life or death are just another form of orgy for the Dark Eldar.
* They also have a nifty device called the Crucible of Malediction, which contains the soul of a psyker who had been tortured to death. Upon activation, the soul's dying screams of agony cause such a massive shitstorm in the Warp that it instantly jams all psychic activity.
* Check out this [[SarcasmMode delightful]] paragraph on how the Dark Eldar bring members of their race BackFromTheDead:
--> ''As a cacophony of shrieks rises and falls around the chamber, those installed in the cocoons above slowly feast upon the resonant energies, [[BodyHorror ever so gradually growing back their bodies - skeleton first, then muscle and sinew, then alabaster skin]] until they are whole once more. During times of war, it is common for every one of an oubliette's regeneration pods to be filled with leering, red-raw fiends that shiver and rattle with every fresh scream.''
* The Dark Eldar are ''old''. So much so, they use a mysterious technology to appear young and beautiful. Psykers and Daemons can see through this however, and see them for what they really are: Shambling monsters, that would make a zombie feel good about how he looks.
* [[http://1d4chan.org/wiki/Kheradruakh Kheradruakh the Decapitator]], the intensely creepy Mandrake champion.
** Let's talk about Mandrakes while we're here. More specifically, their special talents for stealth: their skin absorbs light, making them effectively invisible to all conventional forms of visual detection, and they are able to manifest in any place where there is a shadow. [[ParanoiaFuel I'll just let you think about that for a second]].
[[/folder]]

[[folder:'''Necrons''']]
* The '''Necrons''', the ghosts of an entire, long-dead alien race inhabiting cybernetic bodies who intend to harvest every living soul for their gods. It becomes really creepy when you realize that literally ''any'' planet might have a Necron tomb hidden on it. They tend to appear from nowhere without warning. They sometimes kill everything, sometimes spare certain settlements or individuals. Always for a reason.
* The gods of the Necrons, the C'tan. Originally immense beings that fed off stars, they eventually developed a taste for souls instead. One, the Nightbringer, managed to MindRape itself as death incarnate into nearly every living thing. Then there's the Outsider. The insane C'tan that's locked inside a Dyson Sphere. Oh, and how did it get that way? Giant Star God CANNIBALISM.
* The scary parts are scarabs and wraiths. The former form a massive carpet of flying beetles which eat you alive, and the latter are like ghosts. And they come out of the walls. Flayed Ones look like nothing beside them.
* Their weaponry flays off armour, clothing, ''skin'', ''bone'', ''organs''... and this is done ''one layer of molecules at a time''.
* The narrator of the ''DawnOfWar'' games may be [[LargeHam very hammy]], but he did get one thing right: describing Necron technology as loathsome.
* To reinforce this: '''[[Literature/CiaphasCain CIAPHAS CAIN, HERO OF THE IMPERIUM!!]]''' has shot powerful Daemons in the face, engaged [[AxCrazy World Eaters Space Marines]] in duels, and hurled himself boldly towards swarms of Tyranid horrors. (Granted, [[DirtyCoward he would rather have run away]].) He's merely ''scared'' of these. When it comes to Necrons, he is '''flat fucking terrified'''.
* From ''Xenology.''
--->''Unknown artificial artefact. Unlabelled. Structure is analogous to human hand. Compositional tests confirm metal alloy exterior comprises unknown alloys f... "[[MadnessMantra The metal lives. The metal lives. The metal lives. THE METAL LIVES. THE METAL LIVES.]] '''[[MadnessMantra THE METAL LIVES THE METAL LIVES THE METAL LIVES]].'''"''
* ''"Then I beheld the master of this domain and I knew in that moment that I was doomed. Not to die, you understand, but to truly appreciate the insignificance of my being. The Machine God, you see? It's everywhere, it feeds on us. I saw my companions from Cthelmax fed to the machines, their bodies and souls reduced to their component atoms to feed the insatiable hunger of the Machine God (...) It feeds, young Adept! It feeds! If it has turned its attention our way once more then we are naught but food for the gods! Food for the gods!"'' [[GoMadFromTheRevelation - Adept Corteswain]]
* Scariest of all, the Orks - the most violent, belligerent, and brutal species in the galaxy - and the Eldar - possessing psychic might enough to hit the Necrons were it hurts - were both specifically designed to destroy the Necrons. ''They failed.''
* Another fun nugget is the fact that the Tyranids leave some worlds in their path completely untouched. Since this was mentioned in the Necron Codex, the implication seems to be that the 'nids actually ''back off'' from worlds with a Necron presence. Goodness knows what it is the Hive Mind senses as it approaches.
** It's [[NothingIsScarier what the Hive Mind doesn't sense]] that drives it away. The Hive Mind is a gigantically powerful psychic organism - in Tomb Worlds, it probably senses a terrifyingly huge ''void''. Also, another implication: you live on a planet that's got Tyranids coming towards it. You're just about ready to die of terror when... the Tyranids turn away and leave you alone. [[TemptingFate You breathe a sigh of relief and utter "We're safe!"...]]
** {{Lampshaded}} by a late [[http://wh40k.lexicanum.com/wiki/Aun%27taniel Tau Etherial]] who ''held a party'' for the Necrons who drove off a Tyranid Hive Fleet.
* There are also Necron Flayed Ones - they wear human skins and obsessively hoard dismembered body parts because their god's death-curse gave them an insatiable hunger for flesh - and Necron Pariahs, Necrons [[WasOnceAMan created from humans]]. ''[[TheSoulless Who had no souls.]]''
* The new {{retcon}} puts a whole new spin on the Necrons, going from being tricked and mind controlled by the C'Tan to instead [[TurnedAgainstTheirMasters overthrowing them]] and imprisoning them in Necrodermis bodies. Rather than brainwashed drones, the Necrons are now {{Omnicidal Maniac}}s ''who enslaved their own gods''.
** Narm: The betrayed and broken shards of the C'tan are held in fist-size cubes called Tesseract Labyrinths and only allowed out for battle. Necron Lords and Overlords may be given Tesseract Labyrinths to use to capture enemy heroes and monsters as well as a method of rapid elimination. "[[Anime/{{Pokemon}} Nightbringer, I Choose You!]]" anyone?
** And then, there is the one thing worse involving Necrons: [[spoiler: ''[[FateWorseThanDeath Being]]'' a Necron. AndIMustScream does not ''begin'' to describe how horrifying existing is for them, ''at best''. Even becoming an increasingly EmptyShell does nothing to end it.]]
** Worst: [[spoiler: The Ghost Arks were design to carry necrontyr civilians who refused to be turned into soulless robots, there's a reason why Warroirs scream when killed.]]
** The most horrifying quotation about the Necrons applies to their treatment in both fluff:
--> '''Inquisitor Hoth''': ''That man is beset at all quarters by traitors, mutants and fiends is self-evident. But in truth none of these evils shall be our undoing. When the end comes it will be not at the hand of any mortal being of this or any other realm: death will come at the hands of the ancients, those who determined our fate aeons before we stood erect upon the holy ground of Terra and gazed up into the starry night.''
** And with army addition, the true Star Gods are back. All the C'tan shards of the same Star God feel each other and will do anything within their power to reunite and merge. The transcendent C'tan is such conglomerate consisting of hundreds normal shards. It is fully capable to go toe to toe with most powerful Greater Demons and regained most of its personality and intelligence as a Star God. Necrons keep them in what is essentially a Monolith sized Tesseract Labyrinth and yet this thing barely keeps them in check. While somehow Necrons are able to control Transcedent C'tan Shard on the battlefield for a short duration they only use them under the direst of occasions due to risk that they might escape. Yet some of them roam free seeking to revive the old self and bring vengeance on all who oppose them. It is believed that the Nightbringer on Pavonis, Deceiver on Uralan and the Dragon of Mars are the largest shards conglomerates yet encountered.
* One of the worst parts of fighting a Necron force is that no matter what you do, you can never be sure you even "killed" them. A Necron warrior falls, and before you can get close, its body fades away. It is whisked back to an unknown Necron location, gets repaired, comes back and kills you instead. Even if you ''do'' damage a Necron completely beyond repair, or it cannot be recovered, its self-destruct mechanism is designed to look very similar to the teleportation. [[ParanoiaFuel Even if you wipe out a crowd of Necrons, you can never know for sure that they aren't coming back]].
[[/folder]]

[[folder:'''Orks''']]
* Yes, ok, they're the comic relief faction. But Orks are ''brutal''. They love fighting, they only respect strength,and they don't like any other sentient species very much. What do you think this means for the civilians of the Imperium worlds they invade? What it means for the old and sick, the women and children? They are to be butchered without mercy, and the Orks love doing it. They'll get a quick death sure, but the Orks don't respond to reason or pleading. When civilians run from them, that's exactly what they want them to do as it adds to the sport. The recent video game ''[[VideoGame/Warhammer40000SpaceMarine Space Marine]]'' has audio logs telling of how Orks kill civilians with utmost glee and laughter. ''And this is the faction that is played for laughs.''
* The main reason Orks are funny is because we get to see their perspective, where their language is rendered as Cockney football jargon. In other works (like ''Literature/CiaphasCain''), we see what the Imperium sees: gigantic, monstrous creatures in horrid, rusted armor, wielding weapons that shouldn't even ''work'' but still do, coming down in hordes. There's no reasoning with them - they don't even understand what you're saying. Orks don't speak Gothic. You plead for mercy, and they respond with animalistic bellows and the swing of a giant, cruel axe...
** For some visual aid; here's a darker (and, it could be said, Imperial) view of [[http://images4.wikia.nocookie.net/__cb20110728054210/warhammer40k/images/a/aa/Kurguz_the_Marauder.jpg the Orks]].
* How about the fact that once they've invaded, you can't get rid of the Orks wthout exterminating all other life on the planet. Once you kill an Ork, it releases spores, which settle in the wilderness and, eventually, grow up into new Orks. You can beat back an Ork WAAAGH!, have the Imperial Guard and Space Marines move on to the next theater of war, and then, when you least expect it, a green tide of feral Orks come pouring out of the wilderness.
** Some people actually think of it as a benefit since worlds with feral Orks population tend to have competent and somewhat experienced PDF. The same people may actually have resources to infest planets with Ork spores.
* Red makes a trukk go faster! Shootaz are lumps of junk that only work when they use them! Why? Because Orks have reality warping powers that work on the principle of ClapYourHandsIfYouBelieve! It's hysterical! Then you start thinking about [[FridgeHorror the implications of it]]. If some Ork, at some point, figures this out and learns how to work it to a grand scale? The possibilities are ''horrifying''. Granted, it isn't likely to happen, but there is always the chance. [[spoiler: Unless they ''already have.'' The Orks ''love fighting.'' In the grim darkness of the far future, ''there is only war.'' Coincidence?]]
** For an idea of what this means for the [[RedShirtArmy average Guardsman]], there is a story of a Guard patrol that was pinned down for a couple of hours by an Ork with a [[MoreDakka Big Shoota]], the Ork equivalent of a heavy machine gun (which being Orky is made from scrap, has a smoothbore barrel and fires slugs the size of a golf ball). When they finally killed it they were able to inspect the weapon and were surprised to find it had [[FridgeLogic an ass-backward firing mechanism and no trigger]]. How are you supposed to fight something like that?
* What's scarier than an Ork that raise an army for fun? How about an Ork that has a ''plan''? That has the smarts to ''unite'' the Orks and could probably conquer the whole galaxy if he mustered the numbers? Scary thought, eh? [[http://warhammer40k.wikia.com/wiki/Ghazghkull_Mag_Uruk_Thraka Meet Warlord Ghazhkull Mag Uruk Thraka.]]
[[/folder]]

[[folder:'''Tau & Allies''']]
* To think the '''Tau''' are the closest thing to good guys... It's kind of a statement on the universe as a whole that the expansionist, genocidal, self-righteous, fascist maniacs, who in any other world would be considered raw evil, are part of the lesser evils just because of what's on the other side. Even when you take into account that ''Dawn of War'' hints at the Tau using concentration camps and sterilisation on human worlds they conquer. "Join us or we'll kill you" is a lot nicer then "die heretic/xenos scum", even if a no-answer leads to a plasma round to the face. The existance of the Tau is scary in itself. They are basically practical people, with practical solutions (they are fully aware technology is just that, not some hocus-pocus magic spell, are fully able to use AI without fear and have developed a form of plasma weaponry that doesn't fry you, something only the eons-old Eldar have done). However they have just barely begun to explore the galaxy, and it's hinted that they'll eventually lead themselves into extinction because of their Greater Good ideology. That's right, in the 41st millenium common sense will get you ''killed''.
* For such an "enlightened, peace-loving race", the Tau have a habit of joining forces with some unpleasant fellows, such as the '''Kroot'''. Not only are they strong and fast enough to hold their own against creatures as large as Orks, but their entire culture revolves around devouring the corpses of their enemies so that they can [[EvolutionaryLevels evolve]] and eventually take on the characteristics of the things they eat. And this is just the Carnivore, their basic infantry.
** Kroot Hounds are an evolved form of the Carnivore, and are the perfect definition of the term "bird-dog". Look up a picture of one of these things and just imagine it lunging for your throat, its teeth bared and its claws ready to rip open your stomach.
** Krootox: the bigger, meaner, tougher type of Kroot. Looks just as frightening, if not more so. Comes equipped with a huge gun on its back that can take out light vehicles and turn infantry into ground beef. And it's rapid fire.
** Greater Knarlocs are the Kroot equivalent of a T-Rex. This thing eats infantry by the bucketload and can even destroy enemy tanks. Again, [[http://images2.wikia.nocookie.net/__cb20080303213907/warhammer40k/images/b/b8/Greater_Knarloc_Model.jpg pictures are worth more than words]].
** It can be argued that in the crapsack universe that 40k-verse is, a species whose members are "only" flesh-eating mercenaries is practically friendly. Kroot don't even come across as that scary in the ''Literature/CiaphasCain'' novels. The Kroot translator has a bit of a sense of humour and respects the skills of Sorel the ColdSniper even though Sorel killed one of the other Kroot. And in ''DawnOfWar'', they seem to be a bit snarky, with lines like "Your flag is up. Now what?" They're not fluffy bunnies even by 40K standards, but they're not quite ''terrifying''.
*** They aren't even that evil for a normal setting; while they do have a rigid exterior, the above mentioned incidents of evolution gone wrong show that ''not'' eating people would do far worse to them. In fact you could practically see them in an episode of [[Series/StarTrekTheNextGeneration TNG]] where they give the message to not judge a book by its cover.
** Perhaps more terrifying is in the novel ''Kill Team'' where some Kroot invite the [[FiveManBand titular squad]] to join them for a meal, which they are eager to do since they have only been eating meat-free Tau food for a few weeks. It is only when they start to dig in that they realize [[ImAHumanitarian from what animals]] that meat was taken. The shaper in charge then presents [[BrainFood dessert]], and implies that if one of them does not partake, the Kroot will be most offended and may be motivated to add them to their meat locker... Of course, the shaper turns out to be well aware of the human prohibition on eating the (unprocessed) flesh of their own. The Kroot definitely do have a sense of humor, and it is sick sense of humor indeed.
** We would like to now remind you that the native fauna of Pech, the Kroot's homeworld, is pretty much all Kroot-based, because eventually, every species on that planet was eaten by the Kroot, and some of them got ''stuck'' in those forms and eventually took their place. That couldn't have been very nice, realizing that you and your clan are slowly regressing to a feral state, and unable to do anything about it.
*** It should also be mentioned about the time a Tyranid Splinter Fleet attacked Pech. The Kroot managed to fight them off and drove them into the jungles of their homeworld. Some time later, something in the jungles ''drove them '''out'''.''
* Though not as prominent as the Kroot, the '''Vespids''' are also pretty nasty. They're essentially giant flying bugs, but uglier and with more spikes. At close range, they attack by shredding their opponents into little pieces of flesh with claws that can cut through steel. Have fun imagining that.
** Again, though, the Vespid are, by the standards of the series, pretty nice guys overall. They eagerly joined the Tau upon learning that the Greater Good was quite similar to their own beliefs, and their allegiance to the Tau is one of mutual faith and understanding, not the mercenary-employer relationship of the Kroot.
** All Vespid Strain Leaders are equipped with translators call Communion Helms given to them by the Tau. Vespids are the only species in the Tau Empire that require such devices. [[{{WMG}} They are also the species that most quickly and easily accepted integration into the Empire]].
[[/folder]]

[[folder: '''Miscellaneous alien races''']]
* The [[http://wh40k.lexicanum.com/wiki/Hrud#.UK7auYVlkgI Hrud]]. Just the appearance of these xenos alone is enough to be nightmare inducing, and that's not even mentioning the time warping field they produce that ages everything around them.
* The [[http://wh40k.lexicanum.com/wiki/Umbra#.UK7bc4VlkgI Umbra]] may just be the most ''[[StarfishAliens alien]]'' of all the races found in the 41st millennium. It's basically a floating black sphere that can control ''shadows'' and use them as ''weapons''.
* The old Games Workshop website had a page on several deadly flora and fauna found in the galaxy, including a plant that grabs any animal that passes it, stuffs it inside itself, and then instantly digests them and turns them into seeds.
* There are also the [[http://warhammer40k.wikia.com/wiki/Enslaver Enslavers.]] They're a sentient race ''from the Warp'' that can take control of psykers in order to enter the physical world, then mind control non-psykers and destroy their minds to fuel their own power. One White Scar Astartes once recalls a battle on a planet besieged by the Enslavers, who marched ''one million Imperial Guardsmen'' across a ''100-km wide minefield'', straight into the meat grinder of bolter fire that the Space Marines on the other end laid down. And the Imperium knows almost nothing about them.
[[/folder]]

!The Imperium

[[folder:'''Imperial Inquisition''']]
* The '''[[ChurchMilitant Inquisition]]''' has the power to turn all the biomatter on your planet into flammable goop with a word (aka. Exterminatus), command assassins that include psychotic murder machines that explode on death or ones that fire bolts of pure ''anti-soul'', and countless other horrible ways to kill or torture anyone who catches their attention.
* Or the people who don't. Exterminatus has been ordered ''just to be sure'' on more than a few occasions, with any notable people taken off planet for Inquistorial interrogation.
** [[DawnOfWar And now we've seen Exterminatus rendered in a glorious cinematic.]] That day-long sustained bombardment by a ''battle fleet'' ending in a [[EarthShatteringKaboom ''continent-sized nuke?'']] That's one of the ''nicer'' ways for a planet to go.
* The Life Eater virus is a form of Exterminatus which reduces all life, from the largest animal, to the smallest flower, to a rotten sludge, which is ignited with one blast of a superlaser, burning away everything on the planet, even the atmosphere. It has generally fallen out of favor, since it seems to bolster the forces of Nurgle.
* Fortunately for every non-human in existence, the Inquisitors spend far too much of their time engaged in their own philosophical squabbles, demonstrating that near-infinite resources plus no supervision plus being actively encouraged to think of yourself as the divine will of the Emperor is perhaps not the best combination.
** For the rest of humanity, it probably ''is'' a good combination.
* The Witch Hunters have access to a device known as the "Excruciators". This grants the Witch Hunters player [=1D6x10=] bonus victory points, as he horrifically tortures an enemy psyker with them. As if that wasn't bad enough, one article for ''Inquisitor'' states they have versions of this ''the size of a room''.
** The size is irrelevant. An excruciator has wires which dig into your skin and latch onto nerves, then, with some skill and fine callibration, it is possible to make the subject experience just about any degree of pain that is permissible by the way pain receptors work.
* The Inquisition are one of the highest levels of horror. A regular human will fight because he is told to. Humans don't think about what they are doing, they just do. This applies even to Planetary Governors, Space Marines, Starship Captains and so on. The Inquisition not only have to think for themselves, they have to understand what they are fighting, why it needs to be fought, and worst of all, to know and understand the consequences of the actions that must be taken to defeat them. Can you imagine having to learn and understand a Tyranid? Sure. It would be like understanding bugs on Earth. Imagine creating bug spray, including what it does to humans. Now, could you drop that bug spray over the entire Earth, and kill billions upon billions of people, even to save billions more? The Inquisition do. And they watch.
** And there's a horrible side effect of this knowledge:
*** The life cycle of a Inquisitor usually starts as a Puritan full of promise and hope right out of their schola, attached to another Inquisitor and learning the ropes. They learn pretty much right from the start how the GrimDark universe actually works...
*** By the time they're their own Inquisitor they will be bitter {{Combat Pragmatist}}s, using everything they can to win the war against the enemies and traitors of the Imperium.
*** From there, if they survive, it is a very short hop across the [[MoralEventHorizon invisible moral line in the sand]], of which there are plenty: One too many sacrifices for the good of everyone else, succumbing to the temptation of using disallowed artifacts and rituals, one too much distrust of the local population, etc...
*** These Inquisitors will then have become Radicals, still assured they're in the right due to not being able to see their gradual corruption, unable or unwilling to see how statements such as "Use Chaos against Chaos" just doesn't work.
*** Finally, these Radicals will then meet their end as traitors... usually executed by Puritans who'd, if those live long enough, evetually become hypocritics by becoming Radical themselves...
** Popular portrayals of Inquisitors show them as completely uncaring and cruel when it comes to their methods, but a few tidbits of lore hint that many of them are consciously aware of their actions and the consequences thereof, for both the population and themselves. The inquisitor who held off Hive Fleet Leviathan was stripped of his rank, branded a radical and potentially later killed as a heretic, as well as pitted the Orks against the Tyranids knowing full well that the victor rising from the conflict will be greater than the sum of the combined might of the two armies. He knew that this would ultimately cost him his life, his reputation and the lives of millions. But his actions is implied to have saved billions by diverting the attention of Leviathan so the imperium can regroup and form a more lasting strategy.
* And in the truest tradition of 40k, it ''still'' gets worse. The Inquisition labels some threats not "Extremis Diabolus" (Daemonic/Chaos), "Hereticus Abomini" (heretical), or "Xenos Horrificus" (alien), but "obscuras" instead. The first example that springs to mind are the halo devices -- small trinkets of unknown origin, the halo devices are indistinguishable from normal jewelry but somehow make you immortal. Wearing one will slowly start to de-age you until you're once again in the prime of your life. It then starts to sink into your flesh, and at this point you start having nightmares of eating human flesh. Your body slowly becomes stronger and tougher, healing from any wound. The third and final stage continues the process, except now you need to feed on other people to survive and your body starts to twist into something that could almost be called insectine... almost. Not that you'll mind, because by the third stage it just ''won't be you in there anymore''. You're also indestructible and a single atom of ash from your corpse can revive you if it touches blood and an electrical current. And the very worst part of it? These things aren't created by any of the major players in ''40k'' and [[NothingIsScarier nobody knows what they're for or where they came from.]] This, in a setting where Lovecraftian horrors are a known, expected and planned-for occurrence.
* Inquisitor Heldane's face is altered to look like some sort of mutant horse in order to inspire fear.
* It gets interesting when you consider some of the ''Inquisitor'' characters. One of them is slowly being driven mad by the Eldar spirit stone he's nailed to his helmet.
* Their method of interrogation would give Jack Bauer night terrors. They engage in nine "actions" designed to get the desired information, in increasing order of pain and suffering. The first action is simple verbal interrogation. The second is ''a description of the next seven actions'', which get progressively more painful/invasive, until the ninth action is undertaken, involving all manner of torture performed with the sole intent of causing grievous physical and mental agony, with verbal interrogation to follow if the subject survives long enough to spit anything out. Many people break at the first action (given the Inquisition's reputation), and relatively few people persist past the second.
* The Inquisition as a whole. Imagine being an Imperial citizen, in a discussion with a friend. You go on your way home, and then are kidnapped. You end up face-to-face with a '''very''' hostile man in a BadassLongcoat, who gives you an all manner of questions regarding your faith to the Imperium and the God-Emperor. You plead your innocence to no avail, and he orders you to be strung up and forced you into a series of progressively more nightmarish and agonizing tortures. If you confess, you are executed and branded as a heretic. If you don't, the torture continues until you either die outright or confess. But you don't know this. And either way, they will then round up your family, your friends, your work colleagues, and do the same to them, until they feel they have rooted out the source of the taint. And then [[EarthShatteringKaboom they blow up your planet]], [[TheresNoKillLikeOverkill just to be sure]]. Why? Because during that conversation, an Imperial acolyte in disguise overheard something you said and interpreted it as heresy. Oh, and not only is this somewhat justified to protect the Imperium, but they are ''openly and repeatedly praised'' for doing this, because they ''openly and repeatedly do it''. [[/folder]]

[[folder:'''Dreadnoughts''']]
* '''Dreadnoughts'''. A super-soldier is so horribly wounded the only way to save him is to seal him in a life-support sarcophagus. From then on, his entire existence is either sleeping in a deathless trance or rampaging around the battlefield in a walking tank. Now try the Chaos variants, aptly named "Helbrutes", especially the Khorne berserkers: a demon-possessed super-soldier with insatiable bloodlust is so horribly wounded he is wired into a walking tank. When not in battle, he has to be ''chained to a wall'' because millennia of this confinement has driven him ''completely insane.''
** More specfically with the Chaos Dreadnoughts the pilot is generally removed from the 'body' of the Dreadnought when not in combat, and both parts are chained to different walls. Which would indicate that Chaos Dreadnoughts will go berserk without their pilots...
** There's more: the link between the entombed marine and the dreadnought is FAR from perfect and doesn't override input from the mangled body inside. Aiming that nifty assault cannon? The shredded stump of an arm is dragging along the inside of the sarcophagus doing the same motion. Opened your mouth to speak? People may hear a deep, fearsome robotic voice, but inside you're swallowing gallons of freezing, revolting amniotic fluid, and you feel all of it. Forever.
** Also, Defilers. Huge metal spiders made from the technology of Dreadnoughts. Powered and piloted by a demon summoned by dissecting a Space Marine ''alive''. Enjoys ripping people in half. The pilot's hatch itself is chained over, because not even its own side wants it to get out.
** There is a short story collection called ''Into the Maelstrom''. In short, a Space Marine Librarian (pysker) is placed undercover into the titular Maelstrom, the flagship of a Chaos Lord to find out where the lord will attack next. After he is finally given the information, he reaches out and informs the friendly troops of where the attack will be. At that point, he is captured, being told that his information was a fake, and he's just signed the death warrants of a dozen planets and billions upon billions of humans. After he gets knocked out he wakes up cloaked in darkness. Tubes running through his body. He tries to reach out with his psychic powers, only to find them blocked. [[AndIMustScream He then realises that he's been hooked up to a dreadnought sarcophagus]], which hasn't been attached to one of the machines. The sarcophagus can keep a person alive for a near-eternity, and never has to be hooked up to an actual dreadnought machine.[[/folder]]

[[folder:'''The Emperor and Primarchs''']]
* Of course the Emperor himself counts, when you look at him from a right angle. [[PhysicalGod An obscenely powerful]] MagnificentBastard, with enough scientific know-how to create Space Marines, who [[JuliusBeethovenDaVinci manipulated history]] [[TheseAreThingsManWasNotMeantToKnow in ways Man Was Not Meant to Know]]. [[HorusHeresy John Grammaticus]] once saw the Emperor's true self and got freaked out by thinking about it two hundred years ago after the incident. And let's just add that despite wanting the best for humanity, [[WellIntentionedExtremist he didn't shy from sending his armies on human planets that didn't want to join...]]
** The Emperor may be the benevolent protector of Mankind, but that's poor consolation to any one of the ''thousand psykers per day'' sacrificed to sustain his Golden Throne. The precise how and what of the process has never been explained, but it can't be anything normal people would be used to.
*** It's only a few thousand per ''month'', not day. And we know exactly what happens to them. They spend their time in the queue, typically months or even years, in a relatively high state of comfort. They are fed well, treated with respect, offered privacy. There is no screaming, no death threats, in fact no threats at all because most of them are ''happy'' to be there. Then the anointed day comes, a pod has opened and their time is up. With great ritual they are led from their private chamber to the pod, and... Inserted. Cybernetic implants drill themselves into flesh, bone and brain within moments. Tubes are inserted to make sure they are fed nutrients and stimulants to stay alive and conscious as long as possible. Then the energy hits. The Emperor provides the POWER for the Astronomicron, but has no focus, being mostly dead, so his power is first filtered through several thousand psykers, none of whom could realistically bear even a fraction of a percent of it normally, and the next month or so of their life is utter agony as they act as a biological electric conduit. It's implied that when they can no longer take any more and die, roughly a month or two later, there's no clean up because their body is ''disintegrated'' by the raw power coursing through it. And the reason they look forward to this ungodly existence? Because the alternative is a LONGER lifetime of pain, madness, daemonic corruption and ultimate violent death, typically to little or no benefit to the Imperium as a whole.
* The early days of the Primarchs, if you look at it from the Emperor's point of view. So you have your children in a nice safe place, right? Turns out the place isn't safe enough and your kids just ended up in [[{{Hell}} the Warp]] kidnapped by four Space Horrors that ''really'' don't like you. Have a nice time imagining what can happen to them. At least when he found them they were all total {{Badass}}es and even so, when he found them, they weren't all as expected. Imagine rediscovering your children after decades, maybe centuries of not knowing what happened to them, to find that they've been altered by chaos, one a cyclops, one winged, one ''two people''. Chaos gets to everyone.
** They were identical twins which isn't that scary. Alpharius and Omegon were still a single Zygote when they were thrown throughout the warp. The Emporer probably anticipated that one of them may have had a twin.
* Since we're here, why not the Emperor's point of view now? Being hooked up to a life-support machine for ten thousand years, neither alive nor wholly dead and apparently still conscious? Definitely an AndIMustScream scenario. And consider the following. While ensconced upon the throne for ten thousand years, you have been lovingly and happily told what's been going on. Everything you worked for has been turned around, every word you have said taken out of context and re-imagined to fit the ends of the new religion that holds you as god, the same religion you tried to stamp out. Everything you wanted--enlightenment, negotiations with the rare peaceable Xenos race, the pursuit of technology to better humanity, equality and peace through a unified power structure with built in oversight? Are considered insane or evil and can get people the death penalty. Consider everything wrong with the Imperium of Man - IT IS ALL DONE IN YOUR NAME, FOR YOU, AND WITH YOUR 'BLESSING'. As one person put it, "The only sane man in the universe can do nothing but watch everything go to Hell." Then [[WildMassGuessing there are those who suspect]] that [[ThePlan this was part of the Emperor's plan all along...]]
* Two of the original 20 primarchs are completely unknown; all records of them have been wiped out by Imperial decree. One can only imagine what else happened in the past only to be forgotten by the descendants.
[[/folder]]

[[folder:'''Space Marines''']]
* The '''Space Marines''' themselves are incredibly disturbing after reading an in-depth description of the process used to create them - almost twenty extra organs getting surgically stuffed inside them? And eventually getting turned into an inhuman killing machine completely subservient to the military. But the thing that really gets to people is the sheer hypocrisy (intentional on GW's part, we're sure) of creating these Super-{{Super Soldier}}s to destroy anything not human, yet they're so completely altered in mind and body that they're no longer human at all.
** That's actually played with quite a bit. For example, in GrahamMcNeill's ''Warriors of Ultramar'', Uriel Ventris of the Ultramarines compares his life with that of a Planetary Defence Force trooper whose life he saved, deciding that the sacrifice he made by becoming a Space Marine and sacrificing a large part of his humanity was worth it because he was given the chance to be part of something greater - defending humanity from a hostile universe. Chaos Space Marines, on the other hand, often decide that the loss of their humanity was well worth the power they gain from being a genetically-engineered killing machine.
*** An Imperial Guard officer comments on this in Bleeding Chalice when his troops start to feel better because the Imperial Fists chapter have come to save them: "Do you know how they make Space Marines? They take teenagers, right when they're at that age when you think you're invincible and nothing can kill you, and they give you a gun and armor and send you out to kill in the Emperor's name. If you ask me, they're scarier than the aliens."
** Marines are 7 foot tall, peerless superhuman warriors that spit acid, have bulletproof chests and make [[Franchise/{{Halo}} Master Chief]] look like a paintball player... and that's ''before'' they put on their power armour and pick up their "holy" bolters. To be selected, you must be one of the finest warriors from a planet where life is so brutal that surviving to be a teenager is an accomplishment, (Either a Hive World, a Feral World, or a Medieval World. If you're wondering how bad this can get, well.... it can get pretty bad.) and prove your worth by slaying the local dragon-xenos or in the fires of war. ''Before puberty''. You then undergo training that makes other 40k regimes look soft, filled with brainwashing and worse. You're stuffed with extra organs, including one which alters your genes, rendering you sterile but allowing you to be bigger, stronger, faster, and (hopefully) survive the extra heart they need to grow. Only the toughest achieve this much. Then you get scout armour, and have a trial by fire (which, in the 40k universe, is more like trial by throwing-you-into-the-sun anywhere else). Only then are you accepted as a full marine. Marines are fanatically devoted to their proto-clone and the Emperor and answer to no one alive save their chapter master. They are capable of cleansing a planet on a whim, and more than ready to if they think their pride/honour has been besmirched. And they're touchy. They are portrayed as demigod-like angels of death in Imperial propaganda. Add in a touch of medieval knighthood, chapter-specific influences and even more grim'n'dark and we have a Space Marine. Then things get worse.
** Variants include the chaos daemonic version, the INSANELY heavily armed & armored version (as if their rapid-firing RPG wasn't enough, along with their RPG pistol sidearm), the Viking werewolves berserk version, the fire-crazy dragon-born version, the cyborg version that prays to the god-machine and tends to the souls of vehicles whilst applying nuclear welders to opponents, the bishonen vampire version the hides their thirst for blood & berserker rage underneath their seriously ''beautiful'' faces and more.
** Speaking of the Viking Berserker Werewolves, (The Space Wolves, or Vlka Fenryka, due to an in-universe BlindIdiotTranslation) they're some of the most genuinely heroic characters in the Imperium, something that almost makes you think they're not too bad.... but like many chapters, they have their own brands of nightmare fuel.
*** Like the Blood Angels (more on them later) they have their own kind of terrifying insanity: That of the wulfen, in which the wolf in their gene-seed overwhelms them, turning them into werewolves for all intents and purposes.
*** Those giant fuckoff car-sized wolves they ride? Those are also werewolves, strangely enough-the descendants of colonists who used the DNA of arctic wolves to make sure that they could survive on the horrible DeathWorld that is Fenris. But that went either [[GoneHorriblyWrong horribly wrong]] or [[GoneHorriblyRight horribly right]], depending on how you think of it, and the colonists somehow mutated into lupine monstrosities.
** Starting in the second book of the Blood Raven's trilogy, the process of making a regular man a Space Marine is actually detailed. Stuck in restraints in a room filled with disease, you are cut open, have new organs shoved in, have your eyes cut out and replaced, have your brain burrowed into and 'fixed', and a number of other horrors inflicted upon you. Oh, and they don't bother patching you up, mostly to test if you're really strong enough.
** Luckily, unless you're trying to hurt them, you don't need to fear the scariest of the good guys - the [[OurWerewolvesAreDifferent Space Wolves]], who are badass ChaoticGood Vikings with fangs, and the NeutralGood Soul Drinkers, who are mutated rebels but not ''evil'' ones. [[OurVampiresAreDifferent The Blood Angels]], on the other hand, well... just hope they haven't given in to the Red Thirst & the Black Rage.
*** Not to mention the fact that they have a tendency to go complete batshit nuts just before a battle, to the point that they consider having half their bodies blown off nothing more than a flesh wound. Oh, there's also the fact that if they don't have a Chaplain to rein them in they might just start drinking your blood from your still-beating heart.
*** Why do you think they're so noble? They try their hardest to be, to avoid [[HeroicBSOD losing their minds]] and [[GeneticMemory reliving the last memories]] [[NapoleonDelusion of their Primarch before he died]]. They [[FriendlyNeighborhoodVampire are powerful and loyal allies]] once on your side, but [[OurVampiresAreDifferent heaven help you if they're not]]...
*** Whether or not they're on your side isn't quite the guarantee of safety you'd hope for. The Sisters of Battle once fought alongside the Flesh Tearers and local human militia against the orks. The Sisters and militia were surrounded, but the Flesh Tearers fought their way through the orks, annihilating them...and didn't stop. They slaughtered the militia in their frenzy, and the Sisters of Battle retreated rather than fight them.
*** The battle of Gaius Point is horrific for the Flesh Tearers themselves. It was supposed to be a glorious victory that saved the township and restored their honour; instead, because of the Black Rage (something they're affected by worse than any of the other Blood Angels-descended Chapters), it's a dishonour they can't erase and that's turned their allies against them. And nobody would believe them (or care) if they tried to explain, including their fellow Sons of Sanguinius.
** Oh, and remember that bit about the Tyranid Lictors further up the page? The bit about them eating your brain to take your memories? Yeah, the Marines do that too.
** There is a rather large Chapter of Space Marines that have a secret so ''Dark'' that these particular ''Angels'' of Death will actively avoid Inquisitors and only a handful top tier of the inner circle know even a portion of whatever truth caused them to change their chapter colors and live in shame. A Space Marine that is above morality and emotions living in ''shame'' for whatever happened in the Chapter's past. What could have possibly happened to this Chapter? [[/folder]]

[[folder: '''Imperium and general background material''']]
* The very ideology of the Imperium is scary:
-->''[[NietzscheWannabe Every human life is a spark in the darkness. It flares for a moment, catches the eye, and is gone forever. A retinal after-image that fades and is obscured forever by newer, brighter lights.]]''
** Perhaps an example will better define how horrific the Imperium is at heart. The planet Veyna was colonised in 068.M41, and rather than setting it up as the standard "you do X for the Emperor" planet, the Adeptus Mechanicus spotted the lakes of liquid hydrogen on its poles and claimed all the land for a processing plant rather than continue creating their own. Instead of simply placing the inhabitants to live out their lives on a nearby planet, all but the most rebellious (who fought a guerrilla war to no great effect) were herded off to a forge-world and worked to death. No-one in the Imperium who knew considered this anything unusual or unethical in any way.
** On a similar note: ''BattlefleetGothic'' features ships kilometers long, with torpedo bays. Torpedo bays with three hundred meter torpedoes designed to scream across space and cripple a kilometer-long spaceship. And the Imperium loads these things by hand - by chain and pulley. Not because they couldn't do it automatically, but because it is easier to enslave a thousand humans than it is to build loading rails. The Imperium's greatest resource is men: "Give me enough of them and I shall choke up the Eye of Terror."
*** That's actually kind of beautiful.
*** It is often said that the Imperium only has one abundant resource (and they have rechargable solar-powered guns mind you) and that resource is literally human bodies...
** The entire reason why Deathworlds and Hiveworlds work in Warhammer 40k; they export bodies in exchange for supplies. Deathworlds often are recruited into Space Marine Legions or are required to raise Imperial Guard regiments. Hive Worlds...best not think about what they do with the bodies.
* The quote page for Quotes/ChurchMilitant. And several other quotes pages as well.
* Now that you've read all this, imagine being an [[RedShirtArmy Imperial Guardsman]]. That is to say, a [[BadassNormal normal person]] armed only with a laser rifle, a flak jacket which you will quickly discover to be almost useless, and training not much different from the modern military and tell me the entire ''Warhammer 40k'' universe isn't out to get you.
** It doesn't help that military propaganda says every guardsman is expendable...
*** Oh, and, hey, Guardsman, you know that gargantuan, ravening daemon you just took down, staring seething madness in the face as you stood firm against its foul emanations? Are you imagining medals and a kegger? Well, unfortunately, you were fighting alongside the Imperium's top daemon hunters, the Grey Knights. Of course you didn't know this because they keep their existence secret, and will continue to do so by executing you and your entire regiment. So sorry.
** Now imagine being a member of the PDF, who are the people used to ''buy time'' for the Guard. The RedShirtArmy ''for'' the RedShirtArmy. Not only are you screwed, you don't even have enough training to reduce your degree of screwedness.
*** Note that PDF isn't just a bunch of incompetent fools. This is a regular army of a normal society of the 40k. They train hard, they have competent officers, their equipment is mostly the same as in the Imperial Guard. They have the very same body armor, lasguns, heavy weapons teams, artillery and tanks. It is the best their world has to offer to protect itself. It's just not enough. It's not even close to be enough.
** Though some PDF, mainly from wealthy and/or important worlds (''especially'' Forge Worlds), can be as well or even better equipped and trained than the Imperial Guard. Still, though, most Forge Worlds have permanent, massive IG garrisons, not to mention the Adeptus Mechanicus' legions of cybernetically enhanced warriors (who are far ''more'' capable than the IG, or should be; they're not dealt with much in the fluff). Some worlds, though, have a massive industrial complexes which are extremely important, and with production schedules stretching ahead decades, but don't necessarily make the worlds they sit on Forge Worlds, nor important enough for a permanent IG presence. These are the worlds that tend to have excellent PDF's, simply because they can manufacture lots of top-tier (by human standards) equipment. Wealthy worlds, those with large noble populations or extremely lucrative trading or corporate worlds generally have enough money just to pay for very high quality PDF's.
** The amount of horror varies depending on who you're fighting. You can pretty much expect Orks to just kill you. Tyranids will usually just eat you. Eldar generally just kill you if you're in their way (whether killed by their hand or by the hand of another faction they influenced to attack you). Tau might even take you prisoner ''without'' doing horrible things to you; hell, you might even get to join their club if you don't mind being a second-class citizen and never seeing the Imperium again, because if you do, they'll brutally slaughter you as a race traitor. Simply being shot/eviscerated/turned into a pile of shredded flesh isn't really so bad considering what would happen to you if some of your foes feel like taking prisoners, especially the Dark Eldar or followers of Slaanesh...
** Note that a lasgun is considered to be, more or less, a slightly better modern day assault rifle. A flak vest is considered to be roughly the same as combat armor worn by most modern day advanced troops. In fact, it might even be said that it's ''better'' since it's stated that they're capable of withstanding light machinegun fire, which is already way better than the bulletproof vests that modern forces use (that only reliably stop pistols and shotguns). They are literally the best of our troops transplanted into the Horizon-line-dancing, cosmic wedgied universe that is 40k. And they die in ''droves''.
* That's not to say the horrors are confined planetside. The great space fleets have their own worries, on top of the ones that we already know about space travel. Just to start, space hulks. Lumbering conglomerations of asteroids and ships that may or may not be infested by xenos/demons/things too horrible to imagine. Oh, and since they can also contain priceless technology, there are always plenty of volunteers to board it and look around. And did we mention that these things (Space Hulks) are bound to a) Contain Orks, b) ChaoticEvil Superhuman Soldiers and their demonic friends c) be the bastard child of ''Film/EventHorizon'', ''Film/{{Aliens}}'', ''Franchise/DeadSpace'', and every other movie where a crew goes on a ship and things get bad fast, d) Something Worse, or e) All Of The Above?
* ''DarkHeresy'''s introduced the appropriately-named DeathWorld Phyrr, which makes Catachan look like a cakewalk. To put this in perspective, Catachan is a jungle world on which most organisms--including plant life--are carnivorous (which includes insects the size of heavy tanks and explosive amphibians), and living past the age of ten is a major achievement. Phyrr is a planet on which all organisms are lethal to non-native life, down to a ''genetic level.'' A handful of mere spores from any species of native plant life can kill a man within an hour, assuming that he isn't killed any number of carnivorous or toxic beasts first.
* While we're on the subject of Imperial worlds:
** The entry below, while doing a good job of describing the life of the average Imperial citizen, does not do the average [[CityPlanet Hive World]] justice. They're lawless, corrupt, dirty places like the [[http://weburbanist.com/2008/09/28/abandoned-buildings-places-towns-cities-asia/ Kowloon Walled City]] [[UpToEleven taken up to roughly 21]], with no rules, no law to speak of, polluted to the gills and damn near uninhabitable once you get deep enough due to thousands of years of pollution, and you're constantly at risk of alien invasion, murder at the hand of a horrible gang, or the Imperium itself. Either you'll get caught in an Imperial culling where they kill citizens to keep the population at manageable levels [[note]][[http://wh40k.lexicanum.com/wiki/Hive_World yes they actually do this]][[/note]] and die, or join the army or Space Marines (Their aforementioned horror notwithstanding.) and then die. Why would the denizens of a dirty, polluted Hive World be chosen to join the Emperor's Finest and the [[Characters/Warhammer40000ImperialGuard Imperial Guard]], both of whom are expected in incredibly dangerous situations that would on average make us shit our pants? '''Because Hive Worlds are thought to be as dangerous as Feral Worlds'''. Yes, the average Imperial citizen lives in an environment considered as dangerous as a jungle in the stone age, except the inhabitants have guns and worse.
** And Forge Worlds, worlds dedicated to production of useful goods, are like Hive Worlds but worse because they have even more pollution, and they're run by the Adeptus Mechanicus. If you've gotten this far, you should know why that's a bad thing, but to elaborate they rival the Administratum for being callous bastards.
* Every single little detail about '''{{Psy|chicPowers}}kers'''. Their abilites come from the Warp, so most of their time is spent dreaming about Daemon Worlds with black suns or boiling lakes of blood or clouds of disease and death, or being tempted by the servants of the Chaos Gods with visions of power and suffering and glory and death. The lucky ones are found by the Black Ships (roving fleets that visit a planet every century or so and collect all the psykers present) and killed [[PoweredByAForsakenChild by being "fed" to the Emperor]] to maintain the Astronomicon (the psychic beacon that allows accurate Warp travel). The really lucky ones are [[BurnTheWitch killed in a pogrom]] after their fearful and superstitious fellow humans discover they're a psyker. The unlucky ones are "acquired" by various departments of the Imperium for a particular purpose, ranging from a human communication beacon (the process of creation resulting in, at best, empty eye sockets and often complete loss of sanity), to a Sanctioned or Battle psyker prone to having a daemon hijack their body and soul and even more prone to be executed at suspicion of possession, to the best being allowed the "honour" of training to become a Space Marine Librarian or even a Grey Knight, which involves the aforementioned horrific training of a Space Marine coupled with a healthy dose of MindRape. The ''really'' unlucky ones are not discovered at all, their constant visions driving them to madness and allowing the endless hordes of the Warp to use their skull as a portal and rip themselves into the material realm, quickly consuming the entire planet. If the Enslavers don't get there first. And then there's the Chaos versions...
** ...and then there are Pariahs. Think of every reason you have to not want to be a Psyker, then throw it in reverse, full tilt. You're effectively soulless, cast no light in the Warp and are damned to be an outcast from any and all societies you encounter. At best, you'll end up as an assassin for the Inquisition, or get scooped up by the Necrons to be turned into yet ''another'' form of soulless abomination, half flesh and half necrodermis.
*** Just to iterate a bit further, Pariahs radiate a sensation of wrongness to those around them and generally make people uncomfortable. This means that in a truly CrapsackWorld setting, you can't hold a job, or have a friend, or go to the Emperor's Church (this last one will probably result in the priests labeling you an abomination anyway) - you can't even resort to basic prostitution as only those too drugged out of their minds to notice or those who thrive on your lack of Warp-reflection will "get with you". And if you happen to cross a psyker's path by accident, that psyker WILL take notice of you since your lack of a warp-presence will physically hurt him. Imagine what will happen if you, an extremely rare phenomenon, were to cross the path of a psyker who has some friends very interested in "examining" rare phenomena. Not everyone is [[spoiler:Gregor Eisenhorn]], y'know.
** And then there's Spear, [[spoiler:the Black Pariah]] who cranks the above up to 11 and has a daemon bound to his SKIN.
** Want to know something really scary about Pskyers? They're part of the Emperor's endgame plan: keep himself alive long enough for humanity to evolve and develop enough psykers so that they can fight Chaos on equal terms. The only hope humanity has is for ''the entire race'' to become psykers.
* Here's one from Helsreach, the latest Space Marine Battles novel. [[HumongousMecha Titans]] have a very strong machine spirit, which is constantly seeking to take control of the vehicle, and needs to be kept under control very carefully by its crew. What happens when things go wrong? The Princeps, the commander of the vehicle, ''gets [[MindRape mind raped]] by a HumongousMecha''. Oh, and you now have a two hundred foot tall war machine which wants to kill everything it can see. Have fun dealing with that. It's scary because that borders on FetishRetardant.
* An unconfirmed source from the HumanResources page claims that some parts of the Juvenat Process are derived from children. Yes, that means that the elite of the Imperium and even Literature/CiaphasCain (HERO OF THE IMPERIUM) bathe in children. Blood Countess, anyone?
* "Forget the power of technology, science and common humanity. Forget the promise of progress and understanding, for there is no peace amongst the stars, only an eternity of carnage and slaughter and the laughter of thirsting gods."
* The concept of '''Servitors''' is pretty unpleasant. To elaborate, they are either [[DesignerBabies vat-grown]] [[CloningBlues clones]] or criminals/dissidents/failed teammates who are lobotomized so that they cannot act without bio-programs from the setting's tech-priests. They then have useful [[ArtificialLimbs cybernetics]] attached to their bodies, be they engineering tools, sensors, calculators, or heavy weapons. Since the Imperium has [[AIIsACrapshoot a ban on artificial intelligences]], some servitors are simply [[WetwareCPU wired into vehicles or other machines to serve as semi-organic computers]]. The one saving grace is that there is little enough mind left that the Servitors [[WhatMeasureIsANonHuman are even sentient anymore]].
** Sometimes you actually feel that is not that they are adding mechanical parts to a human body, but that they are adding human body parts to a machine...
** You know where many combat servitors come from? From a system where there is an official sanitarium for Imperial Guardsmen suffering combat trauma. May or may not be a coincidence. Probably not.
*** ...and it's also a main production place for [[FutureFoodIsArtificial Soylens Viridens]] [[ImAHumanitarian is produced]]...[[HumanResources quite probably not]].
** Yeah. Totally a coincidence, considering the near-useless [[http://wh40k.lexicanum.com/wiki/The_Imperial_Infantryman%27s_Uplifting_Primer Imperial Infantryman's Uplifting Primer]] says on page 11 that troopers who break regulation or otherwise fail to meet expectations have the potential to be made into servitors. The overall wrongness of servitors has already been explained, but that adds a whole new level of wrongness. They flat out tell troopers in a BigBookOfWar meant to increase morale that they will be lobotomized, have their identities erased, and be {{Mind Rape}}d into [[WetwareCPU semi-organic computers]] with no free will. And people wonder why the Imperial Guard is a RedShirtArmy on a bad day!
** On the subject of servitors: arco-flagellants. Oh god. Criminals and heretics [[{{Brainwashed}} forcibly re-educated]], [[BodyHorror their arms replaced with horrid powered melee weapons]] like electro-flails, cybernetics all over their wasted forms, [[PsychoSerum drug feeds]] hooked up to their bodies, and [[TheFaceless their faces covered]] [[MalevolentMaskedMen in a blank mask]]. Normally rather passive, kept in a permanent trance of religious images (and this is the ChurchMilitant of the 40k 'verse) and calming thoughts. [[TriggerPhrase Say the word]], and the arco-flagellant goes [[TheBerserker berserk]], [[UnstoppableRage butchering everything in its path]]. As well as the Penitent Engines, devices designed to cause torture [[UpToEleven even worse]] than arco-flagellation. And, to top it all off, the ChurchMilitant seems to think that [[SerialEscalation even these torture devices are not horrific enough, and is always trying to invent new ones]].
*** To clarrify, these are not Servitors, because they don't get mind-wiped. There's still a human mind in there.
*** And why in the Holy Emperor's name did they invent such a punishment? Because Death was ''too good for them''.
** There's also the [[http://wh40k.lexicanum.com/wiki/Image:Cherubim2.jpg Cherubim]], which are flying servitors created out of [[DesignerBabies vat grown babies]]. They often serve no practical purpose, instead being status symbols of the rich and powerful. And no, whatever their creators' intention, they always come out as pudgy, unhealthily pasty little flying angels whose faces tend to be more skull-like than cherubic. Best of all, their brains/bio-programming are derived from animals such as pigs or dogs, so they sometimes go "feral" and make for your throat.
*** There are "better" versions of the Cherubim called Nephilim, which ''are'' made from children. Particularly prized are latent [[PsychicPowers psyker]] kids, even unborn ones, because another psyker can attune to them like a {{familiar}}. Oh, and it has to be a child below the age of 6, or the bones are too heavy.
*** One Tech-priest in the ''Soul Drinkers'' series keeps a number of Cherubim around apparently just to [[UncannyValley unnerve]] everyone he works with.
** Servitor bodies are culled from clones or criminals condemned to death. Do you know what crimes constitute becoming a servitor? Anything from being a SerialKiller to [[DisproportionateRetribution stealing from the temple's donation basket]].
* The '''Tech-Priests''' who maintain them are pretty scary on their own - not only do they occasionally ''replace half their brain with a computer'' to [[StrawVulcan free themselves from emotions]], but they're one of the most powerful forces in the Imperium. This wouldn't be so bad until you consider how many of them are horrible, horrible people - Archmagos Khobotov from ''Soul Drinker'' basically thinks "The Soul Drinkers have an ancient right to the Soulspear, since it's their holiest relic. I don't. ''I'm going to take it anyway anyways''." They literally [[MachineWorship do not care about anything other than the technology]] - [[TheUnfettered no honour, no justice, definitely not other people's lives]]. They will gladly put [[AMillionIsAStatistic an entire world's population at risk]] in order to have a chance to loot a Necron tomb, and tend to act ''offended'' when people wall off Necron tombs rather than letting themselves get annihilated by psychopathic robot skeletons. And they're so powerful ''no-one will ever be able to do anything about it''. Although nice or [[IneffectualSympatheticVillain ineffectual and sympathetic]] versions (like Antigonus in ''[[Literature/GreyKnights Dark Adeptus]]'', Felicia in ''[[Literature/CiaphasCain Death or Glory]]'', Ernulph and Logash in ''[[Literature/CiaphasCain Caves of Ice]]'', also multiple characters in ''Literature/{{Titanicus}}'') do exist - indeed, they probably don't include a higher percentage of bastards than the Administratum - but since their really nasty members are in a position to screw over ''trillions'' of people [[ForScience in the name of the Omnissiah]]...
** It gets better. That [[DeusEstMachina great machine spirit]] the Adeptus Mechanicus [[CargoCult worship]]? Odds are its an EldritchAbomination sleeping inside Mars, and when it wakes up it will literally ''eat the Sun.''
*** Riddle me this: which is worse? The above possibility, or the following? Some say that the Void Dragon is perfectly happy where it is, because it coexists with humanity-- ''by devouring the life-force of every techpriest in the universe through their implants'', bit by bit.
* The '''Warp''', an [[AnotherDimension alternate dimension]] that is [[YourMindMakesItReal literally composed]] [[DreamLand of the worst nightmares of an entire galaxy's worth of humans and aliens]], and is implied to serve as [[SpiritWorld the 'afterlife']] of the galaxy, if not the entire universe. And the only viable method of [[FasterThanLightTravel interstellar travel]] is to [[NegativeSpaceWedgie tear a hole in reality]] and [[HyperspaceIsAScaryPlace send your ship hurtling into this nightmare void]]. Only, in the Warp, the nightmares really can come and get you. Said alternate dimension is made worse by the fact that it is ruled over by the {{four|IsDeath}} [[EldritchAbomination god-like incarnations]] of [[UnstoppableRage Rage]], [[TheChessmaster Deception]], {{Despair|EventHorizon}}, and [[HornyDevils Lust]]. And they all hate you. No exceptions. Even worse is that they could equally be the incarnations of Bravery, Hope, Acceptance and Love...
** Oh, it gets better. One of the older bits of fluff (most likely written before the Horus Heresy series came out) casually mentions that at the dawn of interstellar travel humanity [[UnseenPrototype tried various methods of faster than light travel ]]-'''and going through the Warp was apparently the best option'''. Go on, tell me what could possibly be worse than travel through above-mentioned nightmare world. Oh, don't tell me you can't! This is the 40k verse, if you say [[TemptingFate it can't get any worse]] it's miles ahead of you!
** The 1997 film ''Film/EventHorizon'' is often said to be set in ''[=WH40K=]'', being about a faster-than-light travel experiment that causes the crew to slaughter each other in an orgy of madness and glorification of chaos (lower case). I don't consider that to be the case however, as it is far too tame.
*** After all, the crew basically kills one another when driven insane by the ''visions'' that hell forces on them. In the Warp, sure, that can happen...or you can get killed by the ''actual, tangible demons.''
*** Maybe the ''Event Horizon'' only went into the shallows? Like the Tau do?
*** Canon, inasmuch as there is one, seems to say that the warp drive and the Gellar field were invented more or less simultaneously, in the 15th millennium AD -- that is, well after the events of ''Film/EventHorizon'', which take place in the year 2047. That being the case, the implication is that ''Event Horizon'' incorporated one of humanity's earlier, less successful attempts at FTL travel -- while it's only arguably less harrowing than Warp travel proper, perhaps the system aboard ''Event Horizon'' didn't offer the possibility of protection via Gellar field or anything else, and was thus abandoned in favor of the just-as-harrowing-if-not-more-so option which ''did'' allow for a means of insulating the crew from the horror on the other side of the hull.
* ''Dark Heresy'' gives us this gem, text lifted verbatim: "The Stuff of Nightmares, such entities are completely immune to: poisons, diseases, the need to breathe, environmental hazards, Blood Loss, Stunning, and any critical effect that would not destroy them outright."
** There are some in-universe examples of this in the game itself--a top-level explosive damage critical hit to the head requires any target within two meters of the victim to make a will save or flee for one turn. Likewise, an impact-damage top-level critical to the leg causes agonizing screams to drown out conversation within a 2d10-meter radius.
* Imagine being a common, normal human in this. To paraphrase one of the comic books, "We used to pray that the Emperor would send his angels to save us. Now we pray he never does again."
** To expand on this, imagine being one of quadrillions of human beings alive in the Imperium. Imagine living in a hive planet, which is basically an entire planet hollowed out and turned into a single giant city, where countless other humans live, where all your food and water are probably exported from some agri planet. Imagine being at the mercy of an unthinkably massive government, one that views you, at best, as a resource to be used as they say fit (as a citizen of the Imperium, you have no rights, just responsibilities). On top of some incredibly shitty job (think 12 hours of factory work a day), imagine also having to worry about the incredible amounts of crime all around you. Imagine knowing that, at any moment, the authorities might take you in for any crime (guilty or innocent), and do whatever they please. Imagine being taught from birth that your entire existence is to be a servant to the Emperor, a lesson which everyone around you has learned very, very well. Imagine knowing that any amount of heresy, of any kind, you might display will land you, at best, a very quick death. Then, remember that doesn't account for all the xenos, heretics, and so on that exist all around, and that, with every coming day, the chance of being killed by some invading fleet, your own government, or something similar can only get stronger....Yeah, the Imperium sucks.
** Even more FridgeHorror based on the above (it's starting to look like that the only way to stop running into FridgeHorror is to destroy your fridge. That or carve your brain out with a spoon). For all its innumerable faults and brutalities, the one thing the Imperium can be counted on doing for its citizens is educating them about the dangers of Chaos. Even if said education involves torture and brainwashing. It's drilled into every persons's head from birth to death: the Ruinous Powers are very, very, very, very, very, VERY BAD. It's about an obvious of a statement as "fire is hot". Now take a look at the Lost and the Damned. They're the foot soldiers and cannon fodder for the Chaos Space Marines, made up of traitor Guardsmen, mutants, fanatics... and formerly-Imperial citizens. There's billions of them roaming around at any point and they're the forces of Chaos that the Imperial Guard fight the majority of the time (you know, before the daemons show up and eviscerate them). Here's a great question: what could be SO bad that '''voluntarily joining Chaos is the preferable option?''' How ''desperate'' does someone have to get before thinking that horrible mutations and MindRape is an acceptable price? Even the ones serving involuntarily, could the Imperium be THAT bad that they could be tricked into it? Of course it is.
* Two things that came out in the latest edition that will cause a MassOhCrap moment for any player opposed to Chaos. The Astronomican is going out. AND THE GOLDEN THRONE IS FAILING.
* The little-mentioned '''Ordo Assassinorum''' is ExactlyWhatItSaysOnTheTin. They are a very secretive group that train assassins, with each sub-group or "temple" using distinct methods of assassination. The idea of the vast and powerful Imperium directing their ire at a single individual is frightening enough, but the methods used by each of the temples range from unnerving to outright ''horrifying''. The four major temples are:
** The first is the '''Eversor Temple'''. They "train" Eversor assassins. The Eversor assassins are what you would get if you patterned [[ImplacableMan Terminators]] after [[TheBerserker Viking berserkers]]. Literally kept in cold storage until they are needed, the Eversors are so pumped full of combat performance enhancing drugs that the first augmentation they receive is a boosted immune system just to survive the drugs in the first place. They get aimed at whatever party has offended the Imperium, then shot directly at command centers, the palaces of rogue governors or right into the thick of battle. They proceed to carve bloody, combat-drug infused swaths through the enemy in a psychotic rage, with neruotoxin-firing pistols and anti-tank bombs leaving them capable of destroying anything and anyone in their path to get to whoever they are told to kill. If they survive, they get placed back into cold storage until the next assignment. If not, they explode with a blast capable of killing everyone in the room, the room and the building the room is in.
** The second is the '''Culexus Temple'''. Culexus assassins are created from the Pariahs, people who are literally born without souls. Their mere presence drains the strength from psykers and their weaponry is specifically designed to enhance their psychic-nullifying capabilities, before getting in nice and close, then sucking out their life force. They unnerve normal people, horrify psykers with their mere presence and Eldar Warlocks consider them nothing less than the very embodiment of evil itself. [[http://images2.wikia.nocookie.net/__cb20110926155533/warhammer40k/images/8/8b/Culexus_colored.jpg They have armor to match, too]].
** The third is the '''Callidus Temple'''. Comprised predominantly of female agents, the Callidus use a FantasticDrug called "[[MeaningfulName Polymorphine]]" that lets them change shape into anyone -- ''any''one -- a process that often involves breaking and resetting their own bones as part of the transformation. They're often used for terror tactics and discrete "warnings" -- one famous Callidus is "Mother Python", who stopped a potential rebellion by disguising herself as the elderly nursemaid of the governer's infant son, sneaking into his room, and then using her shapechanging powers to ''distend her mouth and gullet so that she could [[EatsBabies swallow him]] [[SwallowedWhole whole]]'', before escaping, unslowed by the distension of her belly. The disappearance (it's implied she ''digested'' the baby) broke the governer's spirit and caused him to lose any ideas of rebelling. When they do need to assassinate victims, they use a gun that scrambles people's brains and a C'tan Phase Sword, an otherworldly blade that can cut through anything -- even forcefields.
*** Admittedly, this leads to a [[BlackComedy hilarious]] AlwaysABiggerFish incident in the first Necron codex to feature the C'tan; a Callidus attempts to assassinate a person who has already been replaced by the Deceiver. He simply absorbs the blade when she stabs him with it (it's made from the same metal as his body) and then sucks out her life-energy for a snack.
** The fourth, and last of the major ones, is the '''Vindicare Temple''', which produces the absolute best snipers in the Imperium, armed with weapons so powerful they can break an ordinary man's arms with the recoil from one shot, who are capable of waiting completely motionless for days on end in the most ridiculously hostile conditions to make the perfect shot.
* There are two minor subtypes, the Vanus (the intelligence arm), and the Venenum (poison experts short of Chaos and Dark Eldar), which don't seem that bad...but then there's the [[http://1d4chan.org/wiki/Maerorus Maerorus]], which could best be described as Alex Mercer from Prototype. And they're not sure they got all of the eggs to boot.
[[/folder]]

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If any of these images prove to be too much for you, just take a deep breath, relax, watch [[http://www.youtube.com/watch?v=cO3MttgvHUY these]] [[http://www.youtube.com/watch?v=LJMLfACod48 videos]], and take comfort in the fact that {{Narm}} can reduce the scariest of worlds into over-the-top hilarity.