Another scary aspect of Silithus is that the instance it houses, Ahn'Qiraj, is the home of not one, but manyThat One Bosses. One of them, the Prophet Skeram, is very intimidating in himself, while another, General Rajaxx, committed a Moral Event Horizon moment (well, granted, we don't actually see it, but according to the backstory, it did indeed happen) and the last one in the instance, C'Thun, is an Eldritch Abomination who, on top of being one of the toughest raid bosses in the game, whispers ominous things to you as you fight him ("You are weak", "You Are Already Dead", "Your friends will abandon you").
Silithus is so nightmarish as to verge on Scrappy Level status. To say nothing of the constant buzzing...which is enough to make even the least squeamish WoW player's skin crawl.
If you turn up the ambient noise volume in Silthus, you can hear screaming on the wind.
One of the bosses in Ulduar is Yogg-Saron, an Old God like the aforementioned C'Thun. Supposedly without the benefit of being mostly dead already...
As an added bonus, if you went insane, all your friends will look like Faceless Ones, so you have an idea of what your character sees.
A currently unopened crypt near Karazhan has, among its many sections, a huge underwater area filled with dead corpses hanging upside down from huge chains, appropriately named The Upside-DownSinners.
Don't forget the part where if you turn off the music and turn the sound up, you can hear the sound of a muffled heartbeat in the background.
Another creepy part of Karazhan are the opera event bosses Romulo and Julianne. You can tell Karazhan is a messed-up and nightmarish place when it can turn two characters from one of the most well-known plays in Western literature into evil monsters.
Not to mention the "Tonight we plumb the depths of the human soul as a girl tries desperately to get home" narration before...heck, the whole Wizard of Oz opera which does the same thing to Dorothy and the gang.
"Oh I wish I had a heart... Say, can I have yours?"
"Oh at last, at last. I can go home..." * Shudders*
And don't forget the Lovecraftian beasts in the tower leading up to the terrace where Prince Malchezaar waits brooding...the way he always warn new players, "Don't go into the rooms! Go straight to the top!" is like something out of a horror novel.
The notorious Children of Goldshire. The sheer horror is arguably amplified by the fact that - contrary to the other examples mentioned here - Goldshire is supposed to be a friendly and peaceful place, where you certainly don't expect to run into any bone-chilling evil presence.
Fortunately, thanks to the ridiculously high amount of cybering that goes in Goldshire, the Children are pretty much ignored.
Fortunately, or is that part of their plan...?
Read The Tribulations of a Megalomaniac Warlock for a Nightmare Retardant for those children. The writer proposes a perfectly rational, and rather fun explanation for their behavior =P
At certain times of the day in their room, you'll hear a voice clip saying something threatening, usually "You will die." It's in the exact same voice as C'thun.
If you turn up the ambient sound and turn down the music while within the Undercity, disturbing echoes of events from Warcraft III are heard. You will hear tolling bells in the entrance, and then cheering as you proceed along the hallway Arthas did (and those flower petals are still there), and in the throne room (where there's still blood on the floor)...you hear dialogue. The Prophet's warning, and Arthas brutally murdering his own father and declaring his intent to massacre and rez everyone in Lordaeron.
Oh, wanna know the best part about his 'succeeding you' line? If you're possessed of good headphones, because of the stereo channel shenanigans of the throne room's ambience you will hear this said next to and slightly behind your right ear. You hear this line spoken exactly as Terenas would have heard it.
Want to see something fun? Try using a "detect invisibility" sort of spell up in the aboveground courtyard and see the reason why you aren't supposed to cast area of effect spells up there. What could I possibly aggro? you think. There isn't anything here...
Want to see something funnier? Do it in the buildings close to the graveyard, in Duskwood. The ghosts there are about level 50. If you want to mess with a newbie, take him there and dare him to cast an AoE spell. WT Fness guaranteed.
Eugggghhhh...the aptly-named abominations (although "flesh golem" is apparently another canon term) in Undercity.
Fun fact: for the Valentine's Day celebrations, you can go around wooing each city's guards for rewards. If you're Horde, to get the full reward, you need to go and pay a visit to Undercity. Pucker up...
Not to worry, as of Patch 3.3, they've been officially removed from the Undercity, replaced with the Kor'Kron (Elite Orc Guards).
A few Abominations can sort of avoid this, at least as far as personality goes. The ones that are given dialogue can possibly qualify as a weird form of Ugly Cute, mostly since they tend to come off as incredibly childlike and some as borderline innocent. The best example is Gory in the Western Plaguelands, who stays with the Alliance farmers and helps out on the farm and says that that's all he's ever wanted to do.
The silithid hives in Tanaris & Un'Goro, which look like insect hives covered in goo & crawling with bugs.
The giant spiders on Bloodmyst Isle. Most of the giant spiders in WoW actually look rather cuddly. These ones don't. They're just a tad too realistic for this borderline-arachnophobic troper.
And their horrible nails-on-a-chalkboard screeching only adds to their "charm."
Think that's bad? The spiders share a model with Maexxna, a boss from the Naxxramas raid instance. Maexxna's about 50 times larger, though...
On the subject of spiders, the giant Terrokarantula sits in a depression on a ledge on a mountainside -
Go find the cellar at the Ruins of Thundermar in the Twilight Highlands that houses the Black Recluse. When it gets close to death, its little babies come out and play...
There is a quest in the expansion zone of Zul'Drak where a dead serpent god sends you to hex and kill her three treacherous high priests. The hex has a different effect on each one. One is somewhat amusingly 'spun to death'. The other two explode and are quite graphically burnt to death respectively.
The Ghostlands. The second zone Blood Elves quest through. It's always dark and gloomy, there's undead everywhere, the grass and bushes are all dead, and the trees are deformed and covered with glowing mushrooms that, coincidentally, quite often grown in formations resembling upside-down screaming faces.
On the subject of Warcraft, believe it or not, at one point Blizzard was planning on making a game where the orcs would invade the modern-day world; you know, the one we live in right now. They abandoned the idea after they realized such a game wouldn't fit in with the feel of the Warcraft Universe, among other things. A lot of Warcraft fans agree with that move, but then you get hit with the Fridge Logic of what would happen if the Burning Legion did indeed invade our modern-day world. Our nuclear weapons may have worked in World War II, but they would probably just tickleSargeras.
What makes that◊ even creepier is that it's based on "The Colour Out of Space". What would happen to you if you stayed around it for too long? Let's just say that Body Horror doesn't even begin to cover it...
If you think the picture is scary, try watching the way it moves...
In the same area, there's the Matthias Lehner quest chain, which begins with an impossibly long fall into a pit of Eldritch Abominations shambling around. There's a shiny black rock in this area that, upon touching, Matthias tells you "he" is coming and urges you to smear yourself with the horrors' blood to conceal yourself from "him." Once you've done the whole quest chain it's pretty easy to work out who "he" is (Arthas, naturally. Matthias is the remaining sliver of good humanity (that, it turns out, was never particularly good in the first place) within his soul.), but this takes away none of the creepy factor.
The creepy is somewhat mitigated by the sheer levels of awesome in that quest chain, though. Being in the driver's seat for some of the defining moments in Arthas' past, including the fight with Illidan? Priceless. And the whole thing is capped by a Big Damn Heroes moment from the Knights of the Ebon Blade, of all people.
Carrion Grubs and Carrion Worms. You'll find them in the Plaguelands; they are basically gigantic maggots. And the way they shuffle around blindly... * shudder*
It may not be quite that bad - consider the Paradoxical Frog, which is a quite small frog with ten inch long tadpoles.
Before Borelgore was nerfed into being just another quest mob, it was basically an overworld boss fight boasting 60,000+ hp and easily enough damage output to wipe out all but the hardiest groups.
Naxxramas, with the sound up. If you listen closely every so often, you can hear the occasional wail and moan of what sounds like a woman from deep within the instance. It doesn't help to know that the screams are coming from the Abomination Wing, an area used to create... abominations. The final boss of that wing? A towering giant stitched from flesh... of women and children.
A lot of Naxxramas qualifies. The final Spider Wing boss, Maexxna, is a nightmare for anyone with arachnophobia (she is even seen on Naxx's loading screen!). Loatheb has mushrooms growing out of his back, for chrissakes, and just look at his face. Sir Zeliek of the Four Horsemen: what makes him terrifying is that he was once a paladin, now he's a prisoner of his own body, forced to witness how the Lich King uses him to commit crimes against mankind, using his own Holy powers... and poor Sir Zeliek can do nothing but plead. He even tries to warn the players to run upon aggro! And of course the whole Abomination wing, from Patchwerk, to horrifying Grobbulus, to freaky Gluth, and finally to Thaddius himself, sewn as you mentioned from the skin of women and children! The Scourge are monsters.
It might be worth mentioning that Patchwerk sees the whole fight as a game, and the raid group as his toys...
The scream in the background is "help me, save me!" in a woman's voice.
Right after she says save me you can hear a male voice telling her to stop screaming.
There's a few screams. These apparently come from the women and children being used to make Thaddius, and it seems to imply that some of them are still alive inside him. When Thaddius dies, he thanks you, and at that point, all of the screaming in the background stops.
The Legend of Stalvan questline, starting in Duskwood. Basically, a woman tells you that she's had a vision of someone named Stalvan attacking her daughter, and asks you to find out why. You begin investigating, and are left to wonder why, every time you find one of this Stalvan (who, in he first few entries, seems to be a completely normal tutor) guy's diaries, a deranged ghost tries to murder you. Then you keep finding diaries. And you keep reading. And as you read, you're treated to the spectacle of Stalvan slowly but surely losing his goddamn mind, becoming obsessed with one of his students, and eventually butchering her and her entire family, in a brutal murder that's made worse because we don't get to see it, only hear second-hand accounts from people who are still too frightened to talk about it years later. Oh, and, coinciding with the vision that sent you on this nightmare voyage in the first place, all indications point to Stalvan having continued to hunt and slaughter young women on-and-off since then.
And of course, the Curse of Stalvan...
Even his death couldn't stop his killing. You eventually kill him while he's undead, literally living a few hundred feet from Darkshire. In his garden, there's a single flower called Tear of Tilloa (the first girl he killed). Also note that "Tilloa" is an anagram of Lolita.
The Stalvan quests were toned down in Cataclysm, but it's still creepy in a way. This time, you're being asked to find out what's going on by Stalvan's own brother. The contents of the notes are effectively unchanged and there's not ghosts or curses anymore, but still think about the idea of finding out that your brother was a murderer, years after his death.
Then there's the Death Knight starting quests. The backstory - you were a champion of the Argent Dawn, who died fighting the undead and brought back under their control - is bad enough. But as you progress through the quest line, you slaughter innocent villagers, harvest human skulls to help power a plague generator, and torture a random soldier (or, more likely, a lot of soldiers because the RNG hates you/them) for information. And all of this is before meeting a living Argent Dawn member held captive by the Scarlet Crusaders, who you knew in life, and murdering them in cold blood. At least thisfinally starts you on the road to your eventual Heel-Face Turn.
The entire Death Knight starting area is one of the best scripted stories in the game, especially for starting a brand new class, as well as showing off their new "Zone Phasing" tech that moves you seamlessly from environment to environment. You can easily get caught up in the spectacle and then realize that the point of your entire existence is to terrorize and kill innocent men, women and children. As you move through the story you get further exposed to the desperate plight of the villagers, doing anything they can to escape the Scourge. Oh, and The Lich King is whispering things like "No survivors, no mercy" in your head the whole time.
They're not that innocent; this is the Scarlet Crusade we're talking about. Xenophobes being led by demons in disguise.
If you think about it, Kael'thas' transformation from a brutal but well meaning ruler to a twisted, hateful, batshit insane warlord who reveres the Big Bad with a blind, almost loving zeal can be more than a little disturbing. The fact that his lines in Magister's Terrace, including his last words, are little more than insane ramblings and praises to Kil'jaeden does little to help.
Stitches <The Gift From the Embalmer> in Duskwood. A level 35 Elite Boss Abomination that walks the road in Duskwood, and if left alone will eventually assault the town of Darkshire. And there's no real warning that he's coming (unless you're the one who just reached the last step of the quest chain that summons him, or were lucky enough to not be questing (and in Darkshire) when his appearance begins). So you could be coming down the road from completing a quest in the Graveyard, pause for a brief moment because you wanted to look at your map, and then... wham, he's right behind you.
Frostmourne. Decent, kind human beings- including Uther the Lightbringer, a paladin and a good man in every way- are condemned to eternal damnation with no real hope of release purely because Arthas killed them with a damned sword. And they remain conscious and aware.
It doesn't help that it's apparent that Arthas himself may be a sort of case of this. The Halls of Reflection seems to reveal (or at least heavily imply) that Arthas' Orcus on His Throne status may be due to a bit of resisting mind control. One may go so far as to venture that Arthas was equal parts inhuman monster and in a state of And I Must Scream.
In Warcraft Legends (Volume 5, "Nightmares", I believe), Jaina dreams of following Arthas instead of leaving his side at the Culling of Stratholme. Her dream-self does all the things that Arthas would've done himself, such as incinerating innocent townspeople with her fire magic instead of having Arthas crushing them all with his hammer. All the things Arthas did, Jaina performed instead to keep Arthas from sliding down the evil path. In the end of her nightmare, Jaina grabs Frostmourne herself to keep Arthas from ever becoming the Lich King. All well and good, except that SHE becomes the Lich Queen now, saying how she did all this for her beloved Arthas, and will make him the FIRST of her many undead. Her nightmare ends with Jaina screaming in the inside of her in-dream possessed body which just screams And I Must Scream.
The Lich King is already a major prick with nigh-invincible armor, soul-claiming sword, and helm that controls ALL of the Scourge. And Arthas was just a corrupt Paladin/Death Knight. Nigh-invincible armor, soul-claiming sword, helm that controls ALL of the Scourge, MIXED with Jaina, who's already a powerful sorceress... Well, glad ol' Arthy took the sword.
Jaina wielding the Frostmourne would be significantly less of a threat than Arthas wielding it. Remember, Arthas had tons of training with swords and weapons with Muradin and the Silver Hand, Jaina's probably got no idea how to even swing a sword without losing her balance.
The eventual fate of Bolvar Fordragon is very creepy. Having apparently been burned to a crisp by the Red Dragonflight during the Wrathgate he's now spending his time as an eternally burning but fully conscious undead. It's unclear whether or not he feels pain.
That might make it hurt more, since applying ice directly to burns makes it worse.
Word Of God: No one knows where the shards of Frostmourne disappeared to...
Mind Flay. Think about that for a moment.
For that matter, Mind Blast. From what it seems like, it's an explosion of dark power inside your head.
Or Soulfire. It LOOKS like a mere pyroblast, but it is implied to burn the victim's soul. Several other warlock spells qualify, especially affliction spells. An Affliction warlock's speciality is to kill the victim slowly and painfully and boy, do they do it well. Curse of Agony... Corruption... Unstable Affliction... just the names are enough to understand what an affliction warlock's victim is suffering.
To the uninitiated, or those who don't think about it...Curse of Agony essentially sets every nerve in the target's body on fire, Corruption does awful, unspeakable things to their body, likely melting things, Unstable Affliction similar...and then there's their ability to light anybody they please on fire.
The Scholomance. More precisely, the history of the Scholomance as told by the ghost of Eva Sarkhoff at Caer Darrow. Even more precisely, how she tried to hide from the horrors that slowly creeped into the estate, failed, and was experimented on and tortured while magic kept her conscious and alive. Including in the end when ghouls feasted on her body. Finding the chamber of Doctor Theolen "The Butcher" Krastinov only added to this. At least you can kill him, even if he was a pretty difficult boss back in the day.
The Prophet Tharon'ja. The skeleton of a wind serpent (Quetzalcoatlesque winged snake). During the fight she steals your flesh to regrow hers and turns you into skeletons!
That, however, is a perfect example of Cursed with Awesome, because you're given VERY strong abilities when you're in skeletal form.
The Razorfen Downs in the Barrens. Imagine, a mostly dark labyrinth with massive thorn vines hanging overhead. This, in its own right, isn't that creepy, but when you throw in a rather large army of zombies, including undead anthropomorphic pigs and zombified regular pigs (which is quite disgusting if you happen to be eating pork at the time), it gets a little hair-raising. The undead pig-men aren't too creepy in their own right, just how mutilated they actually look, much worse than most other zombies. They pretty much look more like normal pig-men wearing armor made of bacon◊. Then we get to the issue of how this happened. It's sort of implied that the leader of the quilboar people actually sold out her own people to the Scourge, and the majority of the race has no idea it's going on basically across the street.
While not full-on terrifying, the Bone Pile in Razorfen Downs gets a mention thanks to the creepy, nearly demonic music that plays when you enter. The dancing skeletons and the undead Fire Mage screaming words of motivation to them doesn't help matters much.
Remember the little jewel of terror that occurs in the normally peaceful little village of Goldshire, Elwynn Forest. While the entire town, neigh, the entire zone is very serene, there's the one little random spot of horror that is the infamous "Children of Goldshire." To elaborate, in the upstairs of one of the few buildings in town (think leatherworking trainers) there is a back room where you will, on somewhat rare occasions, find a group of six children huddled in a pentagram with one of them in the middle. They don't talk or interact at all, they just...stand there, staring. They will stare in one of a few directions, notably toward Stormwind to the west. When you enter the room, you'll notice that the room is slightly darker than the rest of the building. When the children are there (although I'm not sure if it will happen when they aren't there) you will hear one of several ominous and terrifying voice clips. Most famous is "you will die." Sometimes the children will actually leave the room and run off toward the Valley of Heroes in Stormwind or to the southeast corner of Northshire. When they get there, they'll just stand there, the same boy in the middle, and the other five will form the pentagram again, sometimes changing positions. Worst of all, the event is never explained at all. Speculation is that the Scourge are involved somehow.
Oh, it gets worse. Play the Starcraft II mission on Aiur and tell me that... thing in the screenshot doesn't look like the Overmind.
The old Blood Plague Incident, where a glitch caused an area-specific plague to get out into the rest of the world, infecting and pretty much instantly killing lower levels. Some cities were quarantined, some players, reportedly, went into a Social Darwinist fervor and got infected themselves and spread the disease to low levels just For the Evulz.
Even lampshaded by the friend you must kill as a Forsaken Death Knight. "Don't let the Lich King use you for his evil purposes! ...again!"
If you've ever been to Hellfire Peninsula, you've probably seen a fel reaver. 70-foot demonic robots that stomp around and can be seen from halfway across the zone. If you happen to be in a position where you can't move when you see one, such as when you're eating, your only thought will be "please don't come this way, please don't come this way, please." Of course, there are also the occasions where you'll turn the camera to see one not too far away stomping directly at you. Of course since they walk a certain path, it'll probably turn before it reaches you. It should also be mentioned that they're level 70 elites, meaning that they're elite on top of being 7-10 levels above what most players in the area would be.
Shatter Point, Hellfire Peninsula. An Alliance quest hub. Avoid going there at all costs if you're afraid of heights because it is a small asteroid floating in space over a pitch black and bottomless abyss.
Canted slightly to one side so the ground is tilted.
The Dead Scar is incredibly disturbing, due to its location in the game. Especially to a low level blood elf, who might be unaware of Warcraft lore, traveling across a picturesque, calming landscape, only to suddenly see a hideous black slash of decay and death, populated by rotting cannibals and changed elves...
The quest of Jitters in Duskwood. When you read his journal telling the story of what happened to Sven Yorgen's family. Turns out the Dark Riders came to their house to question them on the Scythe of Elune. They were actually looking for Jitters, since he was hiding out in their barn without their knowledge, but since the Riders didn't know this, assumed the people living there had it. The mother very calmly tries to negotiate the Riders away from her children so they'd kill her out in the woods and then hopefully just go do something else. They then use a mind-reading technique (which according to Jitters' account sounds to be very painful) and determine that Mrs. Yorgen was lying. The lead Rider then orders his men to slaughter the family. When the story gets to this part, Jitters simply says that if he were to describe exactly what happened, he would surely go completely insane. Sven himself, who was in Darkshire when this happened, comes back to find his family's mutilated corpses.
Gnoll tents are made of human skin. There are faces on them.
If you're Alliance, go to the Southern Barrens, the dwarven digsite. Talk to the dwarf in front of the caved in hole in the cliff. They Dug Too Deep. And they found something. They don't say what, but they found something.
It's the Tears of the Moon. It's part of a horde quest given by an exiled dwarf who has a camp hidden nearby. It's EXTREMELY easy to miss (removed after Cata) if you don't simply enjoy exploring maps. Much like the Suntara stones, it's heavily corrupted by the old gods and corrupts the dwarf into a trogg before killing him horribly once you bring it back to him.
Captain Falric in the Halls of Reflection dungeon has a substantial fanbase because of his excellentdialogue and delivery. Until you think about what he's saying...
"[Stood In The Fire]", creepy in more ways than one. The sky turns blood red to signal the *completely random* appearance of the Big Bad and the normal zone music fades out, becoming the tense "Stood In the Fire" track and you hear the roar of the boss, who then begins flying at about the speed of an epic flying mount (380% normal speed) down a set path torching everything: mobs, quest givers, critters, players... nothing survives. But it's not the event that's scary (well, getting "Deathwinged" might be for new players who have no clue as to what happened), it's the suicidal zeal that players have for being there for the achievement.
What's particularly bad about this one is that being in a cave or building, or underground base will not protect you from this event. So if you've spent the past few minutes in a microdungeon, you wouldn't even know this was happening, you'd just suddenly catch fire and die out of nowhere.
It can double as a Crowning Moment of Funny - there's a glitch that renders you immune to the fire if you're on a flying mount and hover just above the ground (you still get the achievement even though you don't die). You get to watch the Mooks of the area respawn and die over and over again for the next five minutes. This troper found it hilarious the first time.
There is another, less common glitch where a player dies to the fire, clicks the button to become a ghost, runs back to his/her body still in flames and notes that they're ghost is making the "taking damage" sound. That's right, this fire is so hot, it burns your soul as well. Fridge Brilliance in hindsight, as Deathwing names himself the Aspect of Death in another zone.
The bears in Hillsbrad Foothills, the ones toward the start of the zone. The bears themselves are not scary, it's the fact that their backs are covered in spider eggs.It's exactly what it looks like.
As of Mists of Pandaria, they may be accompained by infected bear cubs that you can capture as battle pets.
The geist is probably one of the creepiest mobs in the game. Look at one in 3D. Everything about them is so wrong.
In The Sludge Fields in Hillsbrad, one area has "Human Seedlings", people buried up to their neck and completely helpless against the ghouls wandering around. Your character is so horrified by this (Even if you're a Forsaken character), that they help them out of their predicament as a quest.
That isn't the end of it. The quest has a moral choice system: You can either free them by right clicking the shovel you get in your inventory, or right click the Human Seedling to bash their head in with the shovel.
The Ray-Getz-Kalaba Monstrosity is particularly disturbing, especially if you consider the possibility that they're conscious.
If one goes to visit the mountains west of the Deathknell Cemetary in Tirisfal Glades (The Forsaken starting zone) that have been inaccessible since vanilla via flying mount, you'll find a somewhat large forest with a lake and... fairy dragons that dance and sing around a mushroom, it has been untouched by the plague, and is quite lonely. The only wildlife available are small packs of maddened/corrupted deer, and a single, corrupted white "Tirisfal Bear". What is it called? The Whispering Forest. If one has read the lore, you know that the high elves tried settling in Tirisfal, only for many of them to go mad because of something... There is no explanation for anything in the area, leaving only speculation as to what's going on there.
Somebody asked about it in a round of Ask the Creative Development Team, and Blizzard refused to elaborate on it any deeper than "it's not an Old God, but you probably shouldn't go digging there."
Patch 4.3 introduces End Time, showing piece of Northrend after a class-5 apocalypse takes out Azeroth in the wake of Deathwing's victory. It's not even Villain World since the Twilight Dragonflight, left with nothing else to kill, swarm Deathwing and leave his lifeless husk to rot on the roof of Wyrmrest Temple.
Murozond: I have witnessed the true End Time. THIS? This is a blessing you simply cannot comprehend!
The exact event that brought about the End Time, the Hour of Twilight. It is so horrific that simply reading a prophecy about it:turned one of the most pious clergymen in the setting into a ranting, raving psychopath.
In the last quest of the Molten Front, Into the Depths, you are charged with killing Leyara, a Druid of the Flame, you start out with four Shadow Wardens helping you, but after damaging her enough, she starts encasing each Warden in a orb made of flame, destroying them without a body or anything left behind, one by one. Eventually she starts casting it on you, the debuff is called Crushing Flames, "The target in the bubble is crushed until nothing remains but a pile of ash". Hamuul Runetotem just narrowly spared you from getting roasted without a trace.
When you start out the Molten Front quests, the same Leyara burns Hamuul Alive in front of you while you are completely unable to act. She definitely shared her father-in-law's racism towards tauren being in the Cenarion Circle...
Leyara: BURN, TAUREN!! BURN!!!
Deathwing's final form at end of the Dragon Soul raid. After having his armor torn off to expose his molten flesh and shot through the chest with the Dragon Soul, he plunges into the Maelstrom and emerges as a mutating monstrosity. He has completely lost his mind after this and is simply a raving, mindless monster trying to destroy everything around him, complete with his dragon form gruesomely falling apart, to be replaced with a mass of molten tentacles. It's almost a relief not simply to save Azeroth, but to put him out of his misery.
Also, letting Deathwing cast the second Cataclysm. Everyone dies, its your standard wipe... and everything around you is black. Pitch-blackemptiness...
One of the new creatures in Mists of Pandaria are the Sha, creatures borne of negative emotions. The reasons Pandaren are usually calm and peaceful are to prevent the creation of them. They come back due to the erupting war of the Horde and the Alliance on Pandaria. They look... freaky, going by the concept art, they are bony creatures of inky black darkness with a wicked looking smile of sorts. If one looks closely in a stained glass window in Ulduar, there is a painting of what appears to be a Sha. One has to wonder what happened so long ago with the Pandaren to devote some part of themselves to preventing these creatures from reappearing. And what happened to have them be mentioned in Ulduar, if they've been around that long. Especially since Pandaria has been essentially cut off from everything for about 10,000 years.
It gets worse. The murals of Sha in Ulduar might make sense, because it turns out that the Mantid of Pandaria were once the dutiful servants of another Old God called Y'Shaarj, and they shared the world along with the empires of Ahn'Qiraj and Azjol-Nerub. When the titans came and killed 'the Seven Faces of Y'Shaarj', it cursed Pandaria with the threat of the Sha.
And when you're in Sha-corrupted territory, even the sky itself changes, becoming dark and cloudy, and right above your head there appears something like a huge white hole in the sky, looking somewhat like a Forgotten One's maw.
Also in the Jade Forest in Pandaria, there's an old widow who lives alone in a hut. She has a lot of jade statues on her front yard that all look suspiciously lifelike. It turns out that she's a witch that has the power to turn people into jade statues, and by the looks of the number of statues she has, she's been doing it for quite a while. Even scarier when you notice that most of the statues are children...
Darrowshire had a fairly lengthy questline given by a ghost...of a young girl. Who wants her dolly. And misses her father and sister. You manage to make her a new dolly, save her father's soul, and find her still-living sister. It's sweet, triumphant, and one of the creepiest things in the entire game.
In Hellfire Peninsula, on the very edge of the Warp Fields (so on the edge that you need to be able to fly to ensure you won't fall off the edge of the world and die), there is a tiny, extremely well-hidden "jar of ashes". Wrapped around it is a skeleton holding a spear. The jar gives the following message/warning, and the player can only wonder who this was, what happened to him to fill him with such hatred, and what may come to pass if he achieves what he wants.
Here is a jar of ashes. These are the ashes of my sanity, my passion, and my drive. All, utterly destroyed by themselves. May all those who look upon these desolated lands of Hellfire remember this fallen peon. He shed blood for the Alliance, and sacrificed for the Horde only to be driven utterly mad by the wicked and soulless ones who devoured what he held most dear. As they feast from his toils, may they suffer his wrath. Maybe not in this world, but in every world hereafter. It is my declaration, my solemn oath, and my everlasting promise. I will avenge my suffering.
When reaching exalted with the Klaxxi, Kil'ruk the Wind Reaver rewards you with an epic ring, and after explaining about what happened to the Old God they used to worship, he lets you know about this warning, insinuating that the deities that other races worship (like Elune or the Earthmother, for example), might not be what they really are.
"Your gods are not YOUR Gods, outsider. When the Old Gods return, we mantid will once again stand by their side. The wisest amongst you should do the same."
Averted; that was a typo. It's actually "Your gods are not OUR Gods".
The mana bomb that destroyed Theramore was enhanced with the Focusing Iris, the most powerful artifact of the Blue Dragonflight, the guardians of magic. The blast was so powerful it warped the fabric of reality itself, altered the physical structure of anyone caught up in it, and is speculated to have destroyed not just Theramore, but every single possible existence of Theramore in every single possible timeline. Keep in mind that this was a city inhabited mostly by refugees from Lordaeron who helped defeat Archimonde at Mount Hyjal. The only consolation is that it was probably a quick death for those who got caught up in the explosion...
The final quests for Dominance Offensive/Operation: Shieldwall, regarding Garrosh and the Divine Bell...
When you are questing in the Golden Vale and taking care of Mogu, you will see they have Bonfires. Why is this horrific? It's a burning pile of Pandaren Corpses, with some cases of Mogu holding a Pandaren by the Neck over the pile. The sheer brutality is jarring, to say the least.
All of this and no mention of the iconic Plague of Undeath? A sickness that infuses you with dark magic so that you swiftly decay into a corpse, without actually dying in the process, and then places you under More than Mind Control?
And then there's the fact it's totally incurable — those Death Knights in Warcraft III? They used to be Paladins until their inability to cure those infected drove them mad enough to embrace Undeath themselves.
In one of the Warcraft The Roleplaying Game sourcebooks, it's mentioned that attempts to cure the Plague through holy magic have triggered effects like burning the infectee to ashes from the inside out. It's not necessarily canon, but sheesh...
Forsaken Priests have been noted to walk a fine line of sanity at times. Calling on the Light too much can begin to restore their heavily dulled senses, allowing them to feel the maggots in their flesh and smell their own rot.
Eastern Plaguelands. Like all undead areas this one is disturbing but unlike all of them, The place has this sickly orange mist throughout.