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Nightmare Fuel: Castlevania
All the Kings of Evil are decking their castles out with giant rotting corpses nowadays.
Given that the main adversaries in this game are all creatures from mythology or horror movies, it's only logical that there's plenty of frights to be had. One could almost say that the real strength of Dracula's army is its ability to make people soil themselves.
Dracula's castle itself can be seen as one. Due to its always different inner structure in every game, it has been referred by Alucard as a "Creature of Chaos".
In Castlevania: Symphony of the Night, after descending far underground to the deepest part of the castle, you encounter Granfalloon/Legion in the catacombs. It is a Cosmic Horror creature covered in a "shell" of naked, faceless corpses, and they're screaming.
This monster may look both fucking scary and funny at the same time...
Legion returns in Portrait of Ruin, only this time, to add to the nightmare, the bodies fall off as you damage the boss, disappearing into nothing. Try to not think about how those might have been innocent souls you just murdered.
And if you defeat it without shivering, you may eventually make it to the Reversed Castle. Once you get there... well, Beelzebub. Beelzebub is a truly giant, green, rotting corpse with various equally sickening organs showing. It's also grimacing and got long, stringy white hair. It's suspended by chains and meat hooks. And covered with giant maggot-fly-things, which it sends to attack you. They have a way of appearing "close to the screen" when they zoom into the room as well. To top it all off, the arms and legs of the corpse fall off after they have been damaged enough.
The demise of the succubus can be especially creepy. Seeing it in the Saturn version with its original voice-work (which lacks the glorious Narm of the dub) is — well — Alucard is terrifyingly calm as he explains what happens when your astral body dies in a dream, and the succubus starts frantically trying to dissuade him. The screen blacks out, and her scream cuts off. This is the only death in the series you do not see. That makes it so much worse.
If you want to not sleep for a week, consider that she had no idea who the hell he was. No one sent her after you. She chose to do that 'hi im ur mom' routine on her own. Now, given Dracula's attitude toward his wife, and his lack of ability to keep his temper in check (to say the least...) how well do you think he might take some pantsless skankadelic demoness pretending to be her for the lulz? Crossbreed that with his penchant for people on sticks, and then wish they made Clorox for the mind's eye.
Even the Narmy dub can be freaky, as her death cry bounces between pain and orgasm. Damn, don't mock Alucard's momma!
That may explain why Dracula summons her during the Final Boss battle, only to immediately crush her between his massive claws and drink the blood to heal it off.
On the other hand, consider the situation from Alucard's viewpoint and think about what it means to be attacked by a Succubus. By a succubus that's impersonating your mother. If you think winning that fight is nightmare-inducing... The Japanese version even has an alternate game-over voice clip, always a creepy touch, and in this case it's the Succubus saying something like "Let us two wander the eternal darkness together" with a lascivious chuckle.
Shaft. He gets into Richter's brain, which can be horrifically paranoia-inducing. Dracula X Chronicles makes it worse. Look at his hands in the opening cinema, and just try not to shiver convulsively.
Take a good look at Graham's second form near the end of Aria of Sorrow. He is resting comfortably within the heart of two giant pale women with completely exposed ribs and guts, conjoined by the intestines, not to mention the large ring holding them together through their eyes.
And let's not forget how he transformed into... that. After you damage him enough, he rises into the air and screams as his body explodes into a shower of blood that reforms as that giant monster thing. It is disgusting.
In Dawn of Sorrow, there's a really creepy underwater Homunculus enemy. It just sits there until you approach it. Then, it starts thrashing wildly and trying to chase and kill you, while attached to this tube thing that gives it oxygen. That's not the worst part, though. If you don't kill the guy, he'll still follow you. Eventually, if you wander far enough from its spawn point, the tube will stretch too far and pop off the creature's back. The creature will be reduced to spending the last parts of its life thrashing and chasing you and turning purple as it slowly drowns to death.
Some of SotN's songs themselves are terrifying to listen to. Door of Holy Spirits, the background music to the Reverse Colosseum, sounds like something you'd hear in a horror movie. Abandoned Pit has the potential to drive you insane if you're listening to it in real catacombs, and to worsen matters, it's played not only in the normal Abandoned Pit, but also the Cave (the reverse Pit). And should you go through that area, beyond the boss battle with Death, into the Floating Catacombs, you're greeted with Curse Zone, which starts to get more chaotic and freakish at the 0:41 mark. The Symphony soundtrack does a much better job of setting eerie atmospheres than the more cheerful tracks of the later titles in the series. It's like Michiru Yamane became a completely different composer sometime between SotN and Aria of Sorrow.
Castlevania: Dawn of Sorrow features a horrific boss named Gergoth that was apparently chained in captivity for thousands of years in a tower. It looks like a half-rotten dinosaur, with exposed ribs and skin on its face that peels off when it's making an attack. You fight it, seeing its rotten flesh and dripping blood further emphasizing its cursed existence. Made even more disturbing when you read the text in the bestiary and find out it was once gentle, but was driven insane by years of imprisonment.
Castlevania has one decent shock moment (other than the actual final boss) down in the catacombs of a level; red fish men a la Creature from the Black Lagoon jump out of the water in between spaces where the player jumps.
Castlevania II is extremely unnerving for its time. Or — hell, even for now. The gist of it is that you, Simon Belmont, sustained some nasty injuries while fighting Dracula that one time. They're not healing, you feel lousy, and then one morning this guardian spirit appears to you! And she says 'Dracula cursed your wounds, and if you don't exorcise his ghost post-haste, you're going to die and he's going to use your body as his next vessel.'
The Japanese manual is even worse — Simon's not just got unhealing nasty injuries, his body is starting to decay. And the guardian spirit cautions you that the exorcism ritual might not work.
Castlevania III seems innocuous enough. Then you meet freaky monster thing Grant, and find out that Dracula turned him into a megafreak for the lulz. And there's hints that Sypha-the-statue was conscious in spite of being, you know, a rock. There's also the music in the catacombs where you find Alucard.
The JP version doesn't pull aaaaaany punches about Sypha. She says roughly "thank you for helping me, it was starting to seem like I was in danger of being trapped like that forever." Sypha was aware the whole time, and you don't know how long she's been there.
Medusa's death sequence from Castlevania: Portrait Of Ruin. She thrashes around violently while tiny Medusa heads come flying out of her body, then turns to stone, shatters, and falls upwards.
Also, the ceiling of her room features a helpless, petrified commando of modern-day soldiers. Which she shatters when the battle begins.
Castlevania: Lament of Innocence's Bonus Boss, The Forgotten One (imagine Beelzebub from Symphony of the Night in 3D). It is a three screen tall rotting corpse strung on meathooks that constantly moans and roars while you battle it. The fight consists of three parts: its internal organs which constantly spew maggots and poisonous blood, its skinless left arm (the other arm seemed to have rotted off), and its constantly shrieking, horrifically grotesque head.
The buildup to the boss can be scary as well. It doesn't seem to help that the area in which the boss is located is called "The Prison of Eternal Torture", and that you hear a horrifyingly loud, monstrous breathing while you descend the staircase, that only keeps getting louder and louder the further you go. And then you reach a room where the breathing has gotten extremely loud, and there just happens to be blood smeared on the walls and floor. Granted, the main level itself is creepy enough with the high-pitched sound of wailing women as background music.
There's also the Undead Parasite boss and his room (which looks like the belly of some giant monster) and the Executioner enemy, expecially when you see this gargantuan, faceless, cleaver-wielding monster coming out of total darkness in front of you.
Medusa. Her incarnation in the very first game was not bad, but here...
Castlevania64 had The Gardener, a giant, unstoppable Frankenstein's monster armed with a chainsaw that chases you around a hedge maze that you do not know how to get out of. Attacking him enough times stops him for a second before he gets back up and starts chasing you again. And he has no introduction, he just suddenly turns the corner and attacks you.
Also in 64, there's the rose garden. Reinhardt walks into the room and the vampire Rosa is watering roses. She comments how she just waters the white roses. Reinhardt, with a confused look on his face realizes just as the player does that the roses are obviously red. Then the camera zooms into the water pail and you see that Rosa is watering the flowers with blood, and that it has stained them red.
Of the many versions of Symphony's Legion that appear in later games, the one from Aria of Sorrow stands out thanks to its presentation. Several rooms before the boss, you find yourself in an area full of strange humanoids who come out of doors in the background and walk mindlessly forward. They don't damage you; they don't notice you at all. They just keep making a low groaning noise (unsettlingly reminiscent of Zelda's ReDeads). Only when you reach the boss room do you see what's going on: these are corpses being summoned from their graves by Legion to create its shell. At least the original Legion didn't make you think about where the bodies came from...
Order Of Ecclesia keeps its horror modern by adding a new monster based on Sadako. It appears out of nowhere when you get close enough. Anyone who's seen the movie gets a serious jolt the first time this happens.
There's also chainsaw-wielding maniacs they have running around. The HAWHAWHAW laugh they have does not help.
The Wallman. He looks like some sort of Monster Clown from a kid's storybook at worst, and is more annoying than anything. But... the way he dies is some seriously scary Body Horror. His gimmick is he uses glyphs to hide in the wall while you get blown to pieces by bombs. How do you beat him? Simple! Absorb his glyph while he's in the wall and watch him scream as his liquified body sinks to the bottom. And then walk through the wall right afterwards.
Those pallid, constantly-grasping hands in the pits, from Dracula X Chronicles (and perhaps Rondo of Blood as well). Should Richter be unlucky enough to fall/get knocked into them, they grab him and drag him down, their perpetual moaning becoming... something else — and a few seconds later, Richter dies horribly. Since those damn demon hands dragged him offscreen, how is left to the imagination.
After defeating the Golem in Castlevania: Harmony of Dissonance, you find a tall shaft that you can't go up. No problem, there's a switch. You hit it with your whip, hear an ear-splitting shriek, and the room starts filling up with pink liquid. You stay on this rising platform, avoiding spiked platforms, and eventually make it to the top. You look to your left, and see a giant green monster arm crushed under a spiked platform. That pink liquid? It's the monster's blood. You drain a monster's blood to get up a shaft. The arm is disconnected and you never see who it belonged to.
Then there's how you get the Guardian armor pieces. In Clock Tower A, there's a Living Armor, like the one you fought in The Wailing Way A. It has a giant shield, and is invincible to any form of damage. There are two gears embedded in the wall behind it. How do you kill it? Hit it repeatedly until it falls into the gears. It gets ground up, spitting out the armor pieces. What with all the extremely varied and nasty ways things die in this game, it's hard not to wonder if IGA was getting inspiration from Conkers Bad Fur Day.
Don't forget Dracula's final form in that game, which looks like an amalgamation of body parts.
There are two Legion in this game. The first one is the kind we are used to, a "ball" of corpse that we crack open, piece by piece, to hurt its core, and he is named "Legion (Saint)". Much later, we meet up with what "was once his body", the "Legion (Corpse)", which oozes a blue blood and screeches whenever it is hit, before opening the middle section to reveal a corpse that twitches whenever you hit it! And that single corpse in the middle IS the core. Ah, he drops some slithering brains too. Have fun.
The game over screen in Portrait of Ruin's Sisters Mode. Imagine a woman with an eerily calm facial expression as she bleeds out her right eye. That is your motivation for not dying.
The regular game over screen is also scary, showing a bloody skull with a snake in its eyes and a sword in its wide-open mouth.
In Castlevania: Curse Of Darkness, the basement of the Garibaldi temple. As you descend, the walls start literally coming alive until you reach the bottom and they're breathing an pulsing. Not only that, but there are floating bubbles containing concentrated evil in the form of fetuses (called "Evil Cores") that try to suck you into them. At the very end of the hall, there is a door which leads to the Legion bossfight, which is the same idea as the aforementioned Legion bossfight in "Symphony" — a giant ball of corpses. Only here, the entire room is made of corpses. They raise from the ground and, instead of attacking directly, their heads explode on you, causing massive damage...
The music is also scary, reaching its peak as the massive abomination is slowly revealed. Thankfully, the following boss, Nuculais, may be eerie, but is far less scary. Actually, when you see him opening his mouth, he'll fall into the Nightmare Retardant category!
One of the sidequests in Portrait of Ruin involves retrieving "The Statue's Tear". You get the item from a statue of the Virgin Mary in the Nation of Fools. All you have to do is press "up" and a massive amount of blood spills out of the statue.
Lords Of Shadow, the single darkest and most depressing of the series: The idea of losing your childhood love, who was so dear to you for your entire life, to a brutal, tragic death at your own hands, and subsequently suffering a 1000-year life cursed with immortality without her around to heal your emotional wound, just like Gabriel?
Speaking of Lords Of Shadow, the mask of the Necromancer Lord is really creepy. Even worse, it is the brainwashing tool the Necromancer Lord Zobek used to force Gabriel to kill Marie and Claudia. And because the game hates you, the ending credits features a closeup of the damn thing the entire time.
Vampires in this game are quite terrifying. The Mook vampires are bestial savage monsters. The vampire lieutenants are vampirized demons from Hell and look the part. The "child" vampire Laura and her "toys". Of course, they're all pale in comparison to Carmilla's true form. One of the scariest moments in the game occurs in the Vampires' castle. Vampires are pouring out of holes in the ground with no end in sight. Fortunately, there are a couple of big windows nearby and if the drapes are uncovered, sunlight will pour into the holes and keep the Vampires from escaping. All is right with the world. Then, after solving a puzzle later in the level, the sun sets. As night falls, Vampires start coming out in waves...
And then there's the True Final Boss, Chaos, a being of almost Giger-esque incomprehensibility.
Puppet Master in the sequel. Not only is its face horrible, but its attack pattern is scary. It puts a magical puppet into an iron maiden, then swaps Soma directly into it unless you destroy it in time.
There's also Menace, a horrific fusion of all the souls Dmitri absorbs, with plenty of faces where there shouldn't be faces (there's one on his left knee, one inside his mouth, and a full head with an elongated neck as one of his nipples. Also, you're fighting him in an arena made entirely of human bodies, not to mention how he appears, with Dmitri screaming in agony as Menace bursts violently out of his back.
In the first part of the Menace battle, he's trying to stab you with his ribs.