Alveus/Hive, the Big Bad of Season 3 of Agents of S.H.I.E.L.D. is an Inhuman who's become a borderline Eldritch Abomination. He's a Hive Mind being who's impossibly long-lived (he went through his transformation during the Ice Age), can disperse himself in the form of small sand-like insects, and can possess corpses and control other Inhumans. His control acts more like drug addiction, warping his victims' minds into thinking they like working for him. He does this partially because his true form is a creepy monster resembling a fusion between Cthulhu, a human, and an insect. He's insanely powerful, capable of reducing a roomful of humans into flayed skeletons in a matter of seconds and shrugging off any attacks that don't involve fire or electricity. He's also a Merger of Souls and retains the personalities and memories of every person he's ever possessed. He's not really evil, just extremely out of touch with how people actually feel and his Evil Plan is ultimately just a desperate attempt to feel some kind of connection to mortals once again.
American Gods has "Mr. Wood", an ancient former God of trees and forests who saw that the world was moving toward a new age of technology, and rather than fight it, sacrificed his forests to the new world. This allowed him to become one of the New Gods, whose domain is the mass use of wood. Unlike the other New Gods, he has no humanoid form, instead manifesting as prehensile branches and roots from anything made of wood.
"The Tale of the Dark Music": In the Carrs' basement, a small wooden door, between housing the root cellar, holds a black void set with disembodied, red-glowing eyes and a deep, supernaturally echoing voice. Summoned by music, this thing eats people by absorbing them from perceptible existence, and seems able to conjure any given object.
"The Tale of the Magician's Assistant": Nazrak, a shape-shifting demon, seeks, via magician Shandu's wand, to escape "the vortex" and wreck tyrannical havoc.
"The Tale of Watcher's Woods": The titular woods, said to deliberately trap people, are presided over by the Watcher. Manifest as a man wreathed in roots, his woods imprisoned three hikers in a kind of undead suspension.
"The Tale of the Dollmaker": An attic door bridges a life-size projection of a nearby dollhouse's interior. Once inside, entrants are slowly transformed into dolls.
"The Tale of the Curious Camera": To all it shoots, a camera brings destruction. Each photo bears a tiny etching of a gremlin, insignia of some incorporeal culprit.
"The Tale of the Crimson Clown": An ornamental clown doll, with an apparent interest in punishing naughty children, teleports; extends its arm from inside a television screen, and seems able to erase select people from perceptible existence.
"The Tale of Bigfoot Ridge": The Umbra, an incorporeal predator manifest in shadow, drains its victims' vitality and mimics their bodies.
"The Tale of the Silver Sight": A shape-shifting entity, usually manifest as a young boy in Victorian attire, offers the unwary boundless power - with horrendous consequences.
Most of the First Ones on the show qualify, and the Shadows in particular. Their ships basically look like giant pitch-black spiders from hell, and their accompanying banshee scream doesn't improve matters. The first time they are seen in any considerable number is in Londo's dream of Shadow vessels blackening the sky of his homeworld, and his terrified reaction to it says a lot when he is so nonchalant about his other recurring dream, which is a vision of his death by strangulation. Before, humans discover a Shadow vessel buried on Mars and when a member of the team excavating the ship accidentally brushes exposed skin against the ship he died almost immediately.
One of the best descriptions of how incomprehensible the First Ones are comes from the first-season episode "Mind War", after G'Kar saves Catherine Sakai when she goes investigating a planet that G'Kar knows to be dangerous. It turns out it's dangerous because it's the home of a group of First Ones note Though that part is only made clear in hindsight when it's seen again three seasons later as one of the First Ones the Alliance calls upon for help., and when Catherine asks G'Kar about what she saw, he makes the following analogy about an ant:
"I have just picked it up on the tip of my glove. If I put it down again, and it asks another ant, 'What was that?', how would it explain? There are things in the universe billions of years older than either of our races. They're vast, timeless, and if they're aware of us at all, it is as little more than ants, and we have as much chance of communicating with them as an ant has with us. We know, we've tried, and we've learned that we can either stay out from underfoot or be stepped on."
The Made-for-TV MovieThirdspace features a race of ancient aliens that are a kind of Eldritch Abomination, inhabiting a different type of space (neither normal, nor hyperspace) and waiting for a very, very long time until someone finds the Artifact of Doom and activates it, allowing them to be released. Oh, and they have tentacles and extremely strong telepathy, and they cause insanity. Even in the Vorlons. According to the RPG, they move like locusts from reality to reality, devouring and using up each in turn before moving from the ruins of the last to their next prey; the mere psychic shadow of their ancient depredations INSPIRED Lovecraft and analogous authors, not to mention several varieties of cultists, in other intelligent races.
The tentacled monstrosity underneath the Hellmouth is implied to end the world if it were ever released, which almost happened twice, with the heroes barely preventing it.
The tentacle beast ('Hellmouth Spawn') is implied to simply be the creature that lurks in the Hellmouth's 'entrance' (Giles mentions the second time that it's grown since they saw it last) - the world-ending would be caused by all of said creature's Old One compatriots that would also pop through to Earth should the Hellmouth stay open.
Glorificus, better known as Glory, of season 5. Sure, we saw her as a Humanoid Abomination, but that's just because she was a Sealed Evil in a Can. She's a hellgod and was so horrific that other similar gods sealed her and banished her from their dimension. Even in this form, she's an unkillable monstrosity that rips out and eats the sanity from people unfortunate enough to run into her. Technically, she has no name, as she predates language. "Glorificus" is just medieval Latin for "glorious", dubbed by her followers.
Illyria in Angel is from a time when the world was ruled by those like her, who saw (and caused) the deaths of innumerable lesser beings and casually travelled between all dimensions. Before she was De Powered literally nothing the heroes could do even scratched her, and she only abandoned her attempts to reclaim her domain because, essentially, she got depressed. While she spends her appearances in the series possessing Fred's body, her true form is seen in Angel: After the Fall.
Jasmine was so powerful that even summoning her into the human realm required years (maybecenturies) of careful manipulation, and the events immediately before, such as a rain of fire and mass slaughter, were explicitly described as birth pains. Anyone who sees her (even over electronic communication) is overwhelmed with unquestioning devotion towards her and a desire to serve her, which eventually leads to them becoming one with her mind, their own mind overridden by hers, allowing her to control them. Her name isn't even really Jasmine, as her true name can't be spoken by a human and is the only thing that can weaken her.
The Season 8 comics have Sephrilian, Fray gives us Neauth, Boluz, and Vrill, and the EU Dark Horse Comics showed Ky-laag and Azogg-Mon.
The First Evil, the origin of all evil in the Buffy-verse, that existed "before man, before demon", and is said to be within every thought and being in existence. It takes the forms of others because You Cannot Grasp the True Form.
Beljoxa's Eye, that thing from season 7 who told Giles and Anya about The First. It's composed of sentient eyes and lives in a dimension outside time and space. And it's Sophisticated as Hell. It also raises the question of who or what is Beljoxa and, if that's its eye, where's the rest of it?
The Mayor plans to become one. Under the right circumstances, a ritual called "the Ascension" can be used to become a pure demon, of the sort that dominated the Earth during Illyria's era. The Mayor was planning and waiting for over a century to pull this off.
Charmed (1998) had "The Nothing", a creature imprisoned inside another dimension (located in an ice cream truck). It's been put to good use by devouring demon children.
There's also The Hollow, an ancient entity that exists simply to consume power. It can possess any living being and use it to absorb all power. It's said that if it is let loose long enough, it will consume everything. The threat was so great that Good and Evil had to join forces to seal it away. Though, in the series finale, it's revealed The Power of Three can destroy it.
Then there's The Beast, a creature inhabiting the Demon World who devours the spirits of vanquished demons. Human Cole killed it and took all its power.
The Expanse: The protomolecule. In its first appearance it's a squishy and cephalopodic Meat Moss surrounded by occult blue bio-luminescent spores that runs on Human Resources. Then "Critical Mass" proves it's also infectious via Mutagenic Goo, and by "Leviathan Wakes" it has full-on Combat Tentacles and can arrange its spores into a humanoid shape. And even ignoring all of that, it's frequently shown to be a complex lifeform that's only "alive" in a way humans can't normally understand it, and also completely violates the laws of physics whenever it shows up in the story.
Game of Thrones: Robb says Old Nan once told him the sky was blue because they live inside the eye of blue-eyed giant named Macumber.
Ghostwatch, a BBC mockumentary that aired in 1992 and traumatized an entire generation, details a haunting in a house on Foxhill Drive by a poltergeist named "Mr. Pipes". As the show goes on and more insight into the nature of Mr. Pipes comes to light, we learn that the disturbed spirit of the child molester Raymond Turnstall is but one identity of a malevolent entity that has haunted the area for millennia. Worse, the entity commandeers the technology from the broadcast, effectively turning it into a nationwide seance that allows it to reach out and manifest in every home in the United Kingdom.
Helheim Forest in Kamen Rider Gaim is a sentient, interdimensional forest which slowly devours planets.
Evolt from Kamen Rider Build is an alien lifeform that regularly consumes entire planets to grow in strength. His physical "body" resembles a mass of glowing liquid, of which he can split portions off to possess people. The only way he can physically materialize his "true" form is through the aid of external devices such as the Evol Driver.
Already touched upon in the Literature section, but the made-for-TV film adaptation of The Langoliers is pretty traumatizing if you had the misfortune of seeing it as a child.
Dahak from Hercules and Xena is basically the First Evil from Buffy, but without that pesky unwanted intangibility handicap. When Hercules informed a Titan (they fought Dahak in the past) that Dahak was trying to force his way back into the world, the Titan freaked, and put aside her all-consuming hatred of the Olympians to help out Herc.
Invasion Earth, an obscure Sci-Fi UK miniseries, featured the ND, or N-Dimensional Being, a species (or possibly just one immense creature) that as its name suggests, exists in multiple dimensions. That means it can materialise out of nowhere - and the part of it that extrudes into our dimension is huge. It's so virulent and destructive that an entire alien race committed suicide rather than wait for it to destroy them. And now it's found Earth.
In Lexx, the Queen Satellite Worm is immense, obscured by darkness in its underground layer, with glowing tentacles and the ability to shapeshift and take over the minds of humanoids. Its goal is to expand its colony by any means necessary, and humans are simply food to it. We never see it in its full true form, always obscured by shadow, but what was shown was very Lovecraftian. It controls a colony of parasitic mind-raping worms.
The Insects are a whole civilization of moon-sized bugs with an incorporeal "essence" that could be passed on to their offspring or used to possess humans.
Loki (2021) has Alioth, the entity that exists in the Void at the end of time. A massive sentient storm cloud that's shaped to look like a feline skull, it sweeps across the desolate wasteland of the Void, hunting anyone who ends up sent there, quickly erasing them from existence by sweeping over them.
In Lost, you have the Man In Black, who is a pillar of black smoke. Like the previously mentioned First Evil, he can only look human by assuming the form and memories of a person who is already dead.
In the GAROSequel SeriesMakai Senki we are given Gajari, a being that despises humans and Horrors; however, we never truly see what he is except for a head, and apparently his physical body is located somewhere in The Promised Land; from the look of his non-physical form he might qualify as this.
The Outer Limits (1995): In "Monster", a rampaging energy creature is created as an unfortunate side effect of experiments being conducted with people possessing telekinetic powers.
Power Rangers contains a whole stack of them, occurring at a rate of about one per season. There was Lokar, Master Vile, Maligore, Dark Spectre, Queen Bansheera, Master Org, the Master, Omni, Dai Shi, and probably a few others. But one of the greatest things about the Power Rangers is that the vast majority of these characters share a single thing in common. They got the attention of the Power Rangers, and the Power Rangers killed the hell out of them. They've gotta do something about that pesky weakness to giant robots pounding the crap out of them.
An understated one is The Mentor of Power Rangers Megaforce, Gosei. When the newly-minted Rangers question his appearance - a metal face on the wall, only vaguely human-ish - he tells them that it's A Form You Are Comfortable With to communicate with humans. Needing to do that in the first place makes you more alien than your average Rubber-Forehead Aliens or People in Rubber Suits as it is, but needing to do that and this being as close to humanoid as you can manage puts you in far stranger waters.
Dracula in Penny Dreadful; he's a pure demon (Lucifer's brother) and his true form is unknown, though several references to The Dragon of the Bible are said and comparisons with "creatures of the night" (several nocturnal predators like bats and rats).
Darkseid appears in the last season of Smallville and he's possibly even more of an Eldritch Abomination in the show than in the comics. Rather than being a physical being, Smallville's Darkseid is a living cloud of hate, capable of possessing and/or corrupting anyone who isn't "pure of spirit". He's even capable of bringing the dead Lex Luthor back to life. He's also the Beast of Revelations.
In one episode of Space: 1999, Moonbase Alpha passes through a Derelict Graveyard which proves to be infested with one of these.
Star Trek, being a long-running science fiction franchise, is no stranger to eldritch horrors.
The Guardian of Forever from "The City on the Edge of Forever", a sentient Portal to the Past which was physically present for everything that has ever happened. When Kirk asks if it is a machine or a living organism, the Guardian replies "I am both and neither". Apparently, this is the clearest explanation that human understanding makes possible.
Spock: For this to do what it does is impossible by any science I understand.
The Doomsday Machine, of the episode of the same name, is a bizarre ship appears from outside the known galaxy that is irregularly shaped, looking something like a giant cone irregularly carved out of granite, with an abominable eye at its center looking suspiciously like a gateway to hell. It's virtually indestructible and is capable of destroying and consuming whole worlds. Consider also Commodore Decker's response to it: after it destroys his ship and kills his crew, this man, previously an atheist, describes it as the devil and coming straight out of hell and suffers a complete Heroic BSoD. Later, recovering only slightly, his only response is to mindlessly try to attack and destroy it no matter the cost. Failing utterly at this, he is still 'round the bend and steals a shuttle specifically to fly into it and kill himself.
Redjac from "Wolf in the Fold", a formless creature that feeds off pain and suffering. When it possesses the ship's computer, the view screens show a bizarre multicolored, constantly shifting chaos that Kirk speculates is where it comes from.
"The Immunity Syndrome" features an 11,000-mile-long space amoeba that 400 Vulcans (and their computer) could not fathom, drains the life force of every living creature (presumably — and ironically — down to microorganisms) in an entire solar system, and is surrounded by a moving zone of space in which the laws of physics are fundamentally altered.
The Medusans from "Is There in Truth No Beauty?" are so hideously bizarre-looking that to merely glimpse them causes insanity. However, they are completely and unmistakably benevolent, as we see when Ambassador Kollos temporarily borrows Spock's body. The Aesop of the episode, naturally, is about inner vs outer beauty.
The Crystaline Entity from "Datalore" and "Silicon Avatar" is a large, amoral being that the crew can't understand or communicate with, and it destroys every living thing it encounters, feeding on all life on a planet, leaving nothing organic, not even bacteria. (Picard suggests that it might not be evil, but simply a predator which can't comprehend that its victims are sentient, but this view is not widely believed.) It does seem to be able to communicate with Data's brother Lore somehow, who helps it by helping it find victims.
Q. Sure, he seems human enough, but few things ever encountered in the franchise come close to the level of power his kind possess.
On the occasions when humans and similar beings are taken to the home of the Q, the Q Continuum, they are explicitly told that what they perceive is not the reality of the Continuum, but merely a convenient metaphor for something nothing on their level could begin to comprehend.
Species 8472, also known as the Fluidians, the Groundskeepers, and the Undine. Nine-foot tall tripod creatures who come from a dimension known only as "fluidic space", have a triple-helix genetic structure and immunity to just about every pathogen they encounter. They use organic vessels that, when linked, have the power to destroy planets. They don't sleep, they don't eat, can survive in the vacuum of space, communicate with telepathy (being on the receiving end of which is Mind Rapesquared), and have fivesexes. And for the love of God, do not let them touch you. The first race to encounter them were the Borg, a race that nearly wiped out humanity with a single ship. They introduced themselves by attempting to assimilate them. Species 8472 wiped out entire fleets of these ships, and left the Borg begging Voyager for help in the face of being wiped out. In helping the Borg just to survive, Voyager made them regard humanity and the Federation as threats, which Voyager discovered when they found a perfect replication of Starfleet Academy staffed with members of 8472 near-perfectly imitating humans.
The Borg can be considered one to an extent, regardless of being a technological example, having assimilated countless races and technologies in the Delta Quadrant over the course of centuries, stripping them of all individuality and adding them to their collective, travelling in giant cube-shaped ships that are nigh-invulnerable to conventional weapons. And it wants to do this to all races in means of obtaining perfection. Due to their collective nature, killing individual Borg drones is about as meaningful as killing individual skin cells, and even destroying one of their most powerful ships doesn't even qualify as an annoyance. Due to their ability to rapidly adapt to virtually any weapon that's been used against them and render it powerless, they dismiss any opposition as "irrelevant". And they are completely relentless in pursuit of their goal.
The Mind Flayer from Stranger Things is a towering, shadowy thing that inflicts extreme Mind Rape, created and controls the Demogorgons as its foot soldiers, possesses people and animals to fuse together into the massive Flesh Golem pictured above, and may be responsible for turning the Upside-Down into a desolate Eldritch Location. After learning of our world in season two, it's been trying to find purchase on Earth and terraform it to be more hospitable for itself, starting with the town of Hawkins, Indiana. The protagonists never figure out its motives for all this, but speculate that it sees itself as inherently superior to all other forms of life and thus wants to make everything like itself. In an interesting deconstruction, the Mind Flayer is depicted as being less of a truly superior being and more of a petty, hateful creature with a Hair-Trigger Temper. It has pretty much zero tolerance for any sort of pain or setbacks, and seems to throw violent and disproportionate tantrums whenever it's hindered in anyway. That's not to say it isn't genuinely dangerous, but for what is has in strength, it lacks in maturity.
And then in Season 4 we learn that the Mind Flayer is essentially an avatar created by the true villain of the series, Henry Creel/One/Vecna, after Eleven hurled him into the Upside Down. Its rampage in Season 3 wasn't just a temper tantrum— it was a calculated plan to absorb Eleven's portal-opening abilities, and it succeeded, enabling Vecna's plan in Season 4 to bring the Upside Down into Hawkins. Vecna himself also qualifies for this trope: while he Was Once a Man, his experiences in the Upside Down have transformed him into a full-fledged Humanoid Abomination.
The true forms of Angels. Physically, they (to each other) meet the descriptions of them in religious literature. People who look at an angel in his true form have their EYES BURNED OUT. They inhabit human vessels to be able to interact with other humans safely, however.
Castiel: This is... a vessel. My true form is approximately the size of your Chrysler building. Dean: Alright, alright, quit bragging.
Leviathans are referred to by Death in-universe as Old Ones, and Lovecraft was actually inspired by and later killed by one of these things. Their true form happens to be some form of tentacle monster. We're never actually shown their true forms, but they can slaughter angels without breaking a sweat. They're also unique among sentient beings in the Supernaturalverse as being entirely physical beings, having no soul or spiritual form.
Eve, the "Mother of All" qualifies, in that she can disable angel powers, see and hear everything her children do, and custom-build monsters (including hybrids like Jefferson Starships). She's the creator of all of the Purgatory residents above except for Leviathans. The boys had to time travel to find something to kill her, but that probably just sent her to Purgatory, and we know she can get out again.
Death. Initially introduced as one of the Four Horsemen of the Apocalypse, he reveals when Dean meets him that while this is true, he didn't join voluntarily nor was he created for the purpose (implication being that the other three are one of the two), but was bound by Lucifer. He then gives Dean his ring-the key to defeating Lucifer because he considers it an insult to be bound by someone as far beneath him as Lucifer is. In the same conversation, he reveals that he can't remember if he's as old as God or older, and that he will reap God in the end. Before he appeared, his scythe was introduced and shown to be capable of killing reapers, something supposedly impossible. "Appointment In Samarra" heavily implies that he's The Omniscient, though he seemed surprised in a later episode that Sam and Dean wanted him to kill Castiel so how exactly this works is unclear. In "Meet The New Boss", when Bobby protests that they can only open the door to Purgatory during a solar eclipse, Death calmly replies that he'll just make one.
The Season 10 finale reveals the existence of The Darkness, an entity older than the universe, which was only defeated by God and all His archangels working together, and even then it wasn't killed, and had to be sealed inside the Mark of Cain.
Before God and Amara even existed, there was only absolute nothingness. This giant nothing is actually sentient, has a true form that even ANGELS would go mad just from seeing, and its mindset is noticeably more alien than that of any other deity or cosmic entity. Similarly to Lovecraft's Azatoth, it is usually sleeping forever as a mindless entity.
Sentai's baddest is from Dengeki Sentai Changeman. Star King Bazoo looks like a human head and torso, with mechanical parts and exposed organs, larger than the villains' base. His true form is a living planet that eats other planets to grow stronger.
Ninpuu Sentai Hurricaneger has the Evil Will, also known as "It", a shapeless, timeless being of pure darkness with the power to destroy the entire universe if released. It's the end goal of the villains, the Jakanja, to release it so they can use its power to create a new universe In Their Own Image.
Zyuden Sentai Kyoryuger has Deboss, an evil deity known as the "planetary illness" who roams the universe annihilating any species he comes across. He's able to produce monsters from his cells to serve him and has no true form, instead adapting his physiology to suit whatever species he's exterminating.
"Bill" from Too Many Cooks, who chases characters out into the set, tracks them by their above-the-line credits, and replaces them, sometimes several at a time. His above-the-line credit is a blur.
Ultraman feature Bullton, an amorphous "creature" which mess with time and space. A room become loop, inverted gravity, warping stuffs...a mundane facility become Eldritch Location by its mere presence. Worse, what appear to be Bullton is really a projection created by two small meteor fragments.
Another good example is Gan Q from Ultraman Gaia. It is a bipedal giant eye with many smaller eyes all over its body. Coming from another dimension, Gan Q found everything on our side funny, especially when things got destroyed. It also has a Psychic Power that can drive people mad just by sight. Its never-ceasing laughter doesn't help either.
Greeza, the Big Bad of Ultraman X fits this trope to a T. It's most basic form is a hole in the fabric of the universe, but as it absorbs life (its sole purpose), it gains a more humanoid form with a yellow faceless head and purple skin. Its form constantly wavers, warping reality and space-time as if it's a walking spatial anomaly. Its presence creates what is known as Dark Thunder Energy, which turns peaceful Kaiju into raging beasts, increases the power of dangerous ones, and harms Ultramen. It absorbs other life forms into its body using tentacles of energy, favouring Kaiju as its appetizers to absorb their powers. Not helping is its "roar" is a series of psychotic giggles.
The Space Beasts from Ultraman Nexus and the Choju (meaning Super Beasts) from Ultraman Ace could be consider lesser Eldritch Abominations. Both are races of bizarre monsters (often with vague but frightening resemblances to normal Earth things) created to destroy worlds under the command of Humanoid Abominations Dark Zagi and Yapool respectively.
Where In Time Is Carmen Sandiego: Fitting the sci-fi aesthetic that Where In Time had, the mysterious Omnicia got added to the mythos, and it's implied she's one of these. The good news is that she's one of the good eldritch abominations who gives the time pilots helpful information; the bad news is that contacting her is very risky, requiring a lot of power, and is only attempted as a last resort.
Wynonna Earp reveals in its first season finale that one of these, referred to as "the Old One" by Bobo is slumbering beneath the ground just outside the Ghost River Triangle. What we see of it is a mass of tentacles that end in mouths, and its awakening causes the sky to blacken and its blood is enough to possess Waverly. Also, its worth mentioning that the magic barriers of the Triangle — assumed to just be there to keep the revenants in — are apparently actually there to keep this thing out.
"All Souls" involves a series of disabled teenage girls turning up dead... from apparent electrocution through the tops of their skulls. They turn out to be Nephilim (the offspring of angels and humans), and they were killed by a Cherubim sent to bring them back to Heaven. He did this by dropping the illusion he created to protect mortals. His true form is so horrifically beautiful that to see it is for one's soul to be taken directly to heaven.
The humor episode "X-Cops" includes one: a strange entity which changes form into whatever its victim fears the most. It's one of the few monsters in the show to not be drawn from some sort of mythology or urban legend, and is described as more a force by Mulder rather than an actual creature.
