Evil Is Visceral

""The fear of blood tends to create fear for the flesh.""

- Silent Hill

There is something about organic material, especially viscera, being arranged in a grotesque eldritch fashion that is just not right and inherently disturbing/pain-inducing. That makes organic material—internal organs in particular—a favorite representation of evil. There are also things that evil forces make organic, or organic-looking, that really shouldn't be. The usual purpose of this is to Squick people as much as possible.

This trope also covers instances where the mere suggestion that something is like an organic thing—for example, something pulsating as if it was a heart—is supposed to indicate evil.

Subtropes:
 * Alien Kudzu
 * ...And Show It to You
 * Attack of the Monster Appendage
 * Beat Still My Heart
 * Bloody Bowels of Hell
 * Bloody Murder
 * Body Horror
 * Bug War
 * Chest Burster
 * Combat Tentacles
 * Face Full of Alien Wingwong
 * Face Hugger
 * Fan Disservice
 * Fetish Retardant
 * Fetus Terrible
 * I'm a Humanitarian
 * Lovecraftian Superpower
 * Malevolent Mutilation
 * Meat Moss
 * The Plague
 * Synthetic Plague
 * Puppeteer Parasite
 * Tentacle Rope
 * Vagina Dentata
 * Viral Transformation
 * The Virus
 * Virus Victim Symptoms
 * Womb Level
 * The Worm That Walks
 * Zombie Apocalypse

Related Tropes:
 * Alien Blood
 * Big Creepy-Crawlies
 * Brain In a Jar
 * The Corruption
 * Demonic Possession
 * Eldritch Abomination
 * Everything's Squishier with Cephalopods
 * Everything's Worse with Bees—Especially if the bees are shown close-up, and have realistic features.
 * Evil Makes You Monstrous
 * Evil Makes You Ugly
 * Fetish Fuel—Rule 34, Rule 63, and Moe Anthropomorphism can conquer anything.
 * Freud Was Right
 * Good Scars, Evil Scars
 * Gorn—It's okay for things to be blown up and chopped up in disgusting ways if they were already disgusting organic things to begin with.
 * Hive Mind
 * Living Ship
 * Load-Bearing Boss—Sometimes the boss is, literally, the brains or the heart of the place.
 * Ludicrous Gibs
 * Nausea Fuel
 * Organic Technology—Especially if the good guys also have technology. In such an event, the bad guys' technology will be distinctly more organic-looking: wires and cables that look like veins, strangely-rounded shapes that suggest an insect-like carapace, random growths everywhere, people being directly-hooked-up to machines via meaty tentacles, etc.
 * Painful Transformation
 * Reptiles Are Abhorrent
 * Squick
 * Tears of Blood
 * Volcanic Veins

Anime & Manga

 * The bad guys in the Getter Robo series all tend to have this to a degree, but the most obvious ones are the Invader in Armageddon.
 * Guyver—The zoanoids' designs evoke this trope, as well as some of the bioboosted armors.
 * Macross: Do You Remember Love?—This visual element is added onto many Zentraedi things, especially their intelligent/command personnel.
 * MD Geist—The final boss' second form is introduced with a lot of strange fluids, and pulsates and breathes in an organic manner.
 * Nausicaa of the Valley of the Wind—The newborn God-Warrior takes this form, though much of this is due to it being awakened before its time and collapsing into goop as a result. Subverted with the rest of the creatures, when it turns out that humans can live together with them peacefully.
 * The demons in Urotsukidouji.

Artwork

 * H. R. Giger—Much of his artwork is based on this, thus leading to many of the subtropes listed above.

Comic Books

 * Pretty much everything that has to do with The Rot in the relaunch of Animal Man fits this trope. Though it's also subverted, as the series Big Goods tend to use it as well.
 * Vertigo Comics has many, MANY examples of this trope in action. Comics like Hellblazer, The Sandman and Swamp Thing have this trope in spades.

Film

 * Alien series—In addition to creating many of the subtropes, the alien eggs and the visual design of the space jockey are also this.
 * Hellraiser series—Uses this trope in the extreme.
 * Jacobs Ladder—During the hospital gurney scene, many organs are shown laying on the floor, some of which get run over by the gurney.
 * John Carpenter's The Thing
 * Poltergeist—Carol-Ann's closet turning into a squidgy, pink, mucous throat-esophagus sort of thing with a tentacle reaching out to grab her and pull her in.
 * Species—In addition to many other subtropes, part of the horror is simply that the alien hybrids were designed by H. R. Giger.

Literature

 * HP Lovecraft—Many things are "squamous," which means scaly or looking like a close-up of a layer of skin cells.
 * Something From The Nightside—The Big Bad turns out to be a house on the outside but all squidgy and organic on the inside.
 * Additionally, Evil Weapon/Artifact of Doom the Speaking Gun is made out of meat, just to up the "ick ick get it away from me" factor.

Live-Action TV

 * Andromeda—Aspects of the Magog that are not already covered by the subtropes: they spit on people, and have exposed noses.
 * Stargate Atlantis—The Wraith use Organic Technology and are not very pretty themselves.
 * Star Trek—Species 8472, also known as the Undine, are introduced as the only threat to the hitherto biggest threat (the Borg). Their ships are organic and the (CGI) aliens themselves look "more organic" than the usual Rubber Forehead Alien because they don't wear clothes, have extra limbs and strange eyes with complicated irides. Also, they hail from something called fluidic space. To top it all off, the crew of the Voyager are willing to team up with the Borg to fight against them because, well, just because.
 * "Just because" meaning "they can make you die horribly just by touching you, six of their ships can turn a planet into pebbles, and their mission statement is 'The weak must perish.'"
 * The Reavers in Firefly are quite fond of torturing, raping, flaying and eating people, in no particular order. They also favor the visceral aesthetic, like mutilating their own bodies, wearing human skin as clothing and using blood as paint.

Tabletop Games

 * This is very prevalent in Warhammer 40000:
 * Everything about the Tyranids.
 * Many creatures of Chaos have long prehensile tongues and various other features covered by subtropes.
 * Nurgle—The Great Unclean Ones have exposed organs, use their intestines as weapons, use vomit and pus as ranged weapons, etc.
 * Slaanesh—Daemonettes have big crab claws in place of one of their hands, and are rumored to have a nasty surprise instead of normal genitals. Keepers of Secrets are a mix of many different body parts, including breasts.
 * The Daelkyr of Eberron love this trope. From their biological armor and symbiotes, to practicing Body Horror as both science and a hobby. Though said armor and symbiotes can be used for good, if you can overcome their will.
 * Inverted in Splicers. After humanity has lost a Robot War, metal becomes unusable, and so the resistance is based entirely around Organic Technology.

Video Games

 * Abadox is full of this trope.
 * Act-fancer: Cybernetick Hyper Weapon—A sidescrolling arcade game in which you play a morphing biological weapon and fight against an invasion of far larger and far nastier variants.
 * Alien Crush—Two pinball games all about this trope, with an aesthetic heavily inspired by HR Giger.
 * Alien Soldier—Nearly all the enemies and bosses until the last few bosses are this.
 * American McGee's Alice - The Queen's castle is made out of her own organs, with tentacle-like veins acting as walls throuoght the game.
 * Bad Omen a.k.a. Devilish—The final boss is a beating heart.
 * Battle Clash—The design of the ST Valius, the internals of the ST Baron, and pretty much everything about the ST Thanatos all invoke this trope.
 * Bio-Hazard Battle—Pretty much the whole game, especially the organic rocket and the final level. Your characters are Living Ships, so it's not all evil.
 * BIOMETAL—Borderline- The titular enemies may look metallic grey, but they are more like a cross between flesh and metal.
 * Brutal Legend—In the land of Heavy Metal and Heavy Mythril, everything one could associate with Fire and Brimstone Hell is either neutral or good. In particular, Ormagoden, a hellish looking monster Made of Iron, is actually the storiy's Big Good and Crystal Dragon Jesus. Instead, the Big Bad is the Tainted Coil, a race of disease, S&M and Body Horror coated demons.
 * Chimera Beast -- YOU play as the evil visceral creature!
 * Contra series—One of the recurring bosses is a gigantic beating heart. More generally, pretty much anything to do with aliens is this.
 * Cyber Lip—Despite being designed by members of IREM, it provided a major subversion. The Giger-esque aliens in question appear horrific, but are actually allies to humanity. At least before an insane AI brainwashed them..
 * Darkstalkers series—Jedah fights by mutilating himself and using his tissues and blood as weapons(for example, he'll make claws by cutting the joints of his fingers and stretching them in lines of blood, as well as attack with a spray of blood by DECAPITATING HIMSELF). His stage is the inside of a giant womb, complete with giant demonic fetus in the background.
 * The Dead Space series purposely uses as many of the related tropes as possible. Even the creatures and bosses that are not man-shaped at all use organic features for maximum Squick factor. The game studio that develops the games is named Visceral Games, too.
 * Earthbound—Giygas looks like this when the Devil Machine is active. After that... it's a little hard to classify what he looks like, other than pure horror.
 * Gradius series—The final boss in each game tends to be some sort of brain, or a head with a very big brain. The entirety of Life Force is also this.
 * Guild Wars: Nightfall—Especially in the "Gate of Pain" map, which is set in a landscape composed entirely of overgrown viscera, but the whole landscape infected by Abaddon throughout the later parts of the game show signs of this trope, with tentacles and insectoid body parts growing out of the ground, rock formations with eyeballs in them, etc.
 * Metroid series—Mother Brain and the Aurora Units are big brains that do not look very pretty. Starting from the first game, the Metroids themselves have visible blood vessels of some sort. In the second game, they were given an insectoid life cycle. In the third game, one of them grows really big, letting you see even more organic bits inside of the body.
 * Ninja Gaiden series—Almost everything related to demons and fiends, especially the NES games.
 * Psyche Metal—Is all about this trope. Even the main character is a floating eyeball.
 * Robot Unicorn Attack (Heavy Metal Version) -- The foreground islands, except for the layer on which you run, are made of assorted bones, and the background islands are held up by tentacles of some sort.
 * R-Type—All of the advanced forms of the Bydo. This includes and is not limited to: weaponized giant sperm, phallic bosses, bosses that look like vaginas, and on and on...
 * R-Type Final also introduces the B-Series which attempted to make Bydo-like lifeforms which could be safely piloted. Most worked fairly well, but the project also had it's little bumps.
 * Saya no Uta—Lovecraft inspiration, and also because the insanity producing hallucination is that the whole world is... meat.
 * Shadows of the Damned—The game takes place in hell. A very fleshy, organ-splattered hell.
 * Shippu Mahou Daisakusen—The boss of the Dead Forest stage is a naked woman connected to a three-faced Eldritch Abomination via meat-tentacles.
 * Silent Hill series—Many of the monsters are based on this - if not visually, then with their sound effects.
 * Silent Hill 3—The mirror room uses the growth of veins and blood as part of its horror factor.
 * Soul Series—the evil weapon Soul Edge and things associated with it tend to have a flesh-and-bone look, with a pulsating demonic eye as a focal point.
 * Splatterhouse series—Pretty much everything in this game series.
 * Starcraft series—Aspects of the Zerg that do not fit neatly into other tropes: the way that buildings pulsate when they are being constructed, their sound effects (especially if liquids are involved), the Overmind's influence is represented by a big eye. Then there's the growing tissue sample in Starcraft II...
 * Valis 2—Emperor Megas has lots of twisted bundles of huge biomechanical arteries underneath his armor and face.

Western Animation

 * While it's not the case with every villain this frequently comes up with the monsters of Generator Rex.
 * In Spiral Zone, anyone affected by the eponymous zone will begin to develop Meat Moss and "overcome" The Evils of Free Will. However the latter effect doesn't apply to the Black Widows (due to Applied Phlebotinum), resulting in the villains having parts of their bodies covered in red blotches.
 * Majorly subverted in the Young Justice series. The first two-parter seems to play it straight, with hordes of monstrous bio-weapons and Meat Moss covering the lower areas of the lab.

Anime & Manga

 * Irresponsible Captain Tylor—Deliberate use of this trope: see here at 0:49 (slightly NSFW).
 * Lensman anime—The Boskone ships are depicted as more organic than their opponents.
 * Macross -- Guess who's the bad guy.
 * Neon Genesis Evangelion—Possibly both played straight and inverted (slightly NSFW).
 * In Gurren Lagann, the humans and Beastmen use your typical technological mecha and spaceships. The Anti-Spirals have spaceships that look like hands and feet, and their capital ships are basically Star Destroyers with giant human heads on them.
 * It also contains a mild Inversion. As the human mecha all have faces and the first Anti-Spiral units seen, part of the Extemination System, are abstract machines with no organic looking features. They're quickly dubbed Mugan or "Faceless". They still look like Eldritch Abominations though.
 * They also look like Tron rejects...

Live-Action TV

 * Babylon 5 -- As seen here. Granted, some of the good guy ships also had a vaguely organic appearance.
 * Star Trek—Species 8472 wasn't the only alien race that had organic - looking vehicles.
 * Star Trek the Original Series—The Doomsday Machine
 * In later years, there have been a number of "free - roaming space whales" collectively known as Cosmozoans. The Crystalline Entity was a nasty, but many of the others weren't.

Video Games

 * Mass Effect 2—Your ship is all clean lines and metal. The Collector ship is all black monolith tech overgrown by some kind of organic... stuff. The Collectors themselves have an exaggerated insectoid and exposed-muscles look.

Anime & Manga

 * Blue Seed -- Justified in that the Aragami fight by infecting earth creatures and turning them into monsters.
 * Silent Möbius—As seen here at 0:55.