The plot that seemed to be going has been abruptly overshadowed by the revelation that the setting you thought you were reading about is merely an infinitesimal fraction of a universe that actually teems with overwhelming otherworldly menace.
The threat this reveals is likely to virtually overshadow all the more mundane players you already knew about; at the very least, it substantially alters both the reader's and the characters' understanding of their world. The rebellious factions in The Federation are actually being controlled by an unusual artifact, just shipped back from recent excavations in a fringe system. The Corrupt Corporate Executive and Professional Killer are its cultists. The Evil Overlord you just defeated was the Cosmic Keystone keeping it out, or the whole point of his brutal tyranny was to harden everyone for the things to come, or he himself is the eldritch horror.
The plot probably didn't completely Genre Shift into Cosmic Horror Story, but at the very least, it just received a very noticeable transfusion — it could almost be seen as the Cosmic Horror Story genre itself invading the more traditional settings we know, parasitising them, and altering their realities to one that suits it better.
Subtrope of Outside-Context Problem, and sometimes The Man Behind the Man. Compare Genre Shift, Genre Blending, and Going Cosmic. Contrast Giant Space Flea from Nowhere and Diabolus ex Nihilo, wherein the unexpected threat is not necessarily a thing from beyond, and whatever it is is completely unrelated to the extended plot.
Note: This is a Spoilered Rotten trope, which means that EVERY SINGLE EXAMPLE on this list is a spoiler by default and most of them will be unmarked. This is your last warning; only proceed if you really believe you can handle this list.
- Towards the end of Romeo X Juliet, it becomes clear that the true enemy isn't the murderous Lord Montague, who is slowly descending into cackling, city-burning madness, but rather the death of Escalus, which is what's holding Neo Verona in the sky: the earthquakes that become much more frequent and ruinous towards the series' climax are the result of Escalus slowly perishing.
- Digimon Tamers: The D-Reaper turned it into this. Although the numerous Shout Outs to the Cthulhu Mythos may have served as foreshadowing to savvy viewers.
- Puella Magi Madoka Magica: It starts as a typical Magical Girl anime, though with a particularly trippy version of The Heartless. About halfway through the series, it's shown that the Weasel Mascot Kyubey is ripping out people's souls in exchange for wishes. The trope comes in when it's revealed that Kyubey isn't a demon like you'd expect. He's actually closer to an Eldritch Abomination who actually cares very little for mankind and Earth and follows his own Blue and Orange Morality and his own goals.
- The first half of Tengen Toppa Gurren Lagann is spent defeating the Spiral King, only to reveal in the second part that he was protecting humanity from being wiped out by the eldritch-like Anti-Spirals, and in the epilogue, the earthlings are shown heading out to face the even more eldritch-like Spiral Nemesis.
- Kill la Kill starts off with Ryuko fighting the Absurdly Powerful Student Council, led by the dictatorial Satsuki. It turns out that Satsuki was trying to rebel against her mother Ragyo. The Life Fibers that make up the clothing that give people superpowers are actually alien parasites that have shaped the course of human evolution, and Ragyo wants to accelerate their ultimate goal: consume every human on Earth and use their energy to explode the planet, sending new Life Fibers hurtling towards other worlds.
- In Hunter × Hunter, an interesting variation is The Reveal that the human-inhabited world we'd seen so far (which is the size of our own, with comtinents of similar shape and size), which already has copious amounts of incredibly dangerous locations and species (for example, Swindler's Swamp, where the whole ecosystem is geared towards attracting, entrapping and feeding on humans) is only a tiny fraction of the whole planet, and that what little information there is about the rest of the world (called the Dark Continent) paints it as a horrific Death World of incomprehensibly dangerous horrors that dwarf any threat encountered so far by the Shonen protagonists; as a point of comparison, the Chimera Ants, the most powerful menace in the series previously, which were an existential threat to humanity in a world where the potential to be a Person of Mass Destruction is relatively common, are considered the least dangerous of the known species originating from the Dark Continent, and the survival rate of expeditions there, which tend to be extremely well-organized and funded and to include many said powerful individuals, is about 1 for every 2500 people. It's rather obvious that humanity survived this long only because the menaces from the Dark Continent barely pay attention to it for some reason.
- A particularly bizarre Disney comic ("The Call Of C'Russo") that is a parody of the Lovecraft mythos involves Donald Duck winning in a singing contest before it's revealed that he's actually been recruited to wake up an Eldritch Abomination with his voice. The world disappears because it only exists when the monster is dreaming about it, and Donald and his nephews grow octopoid arms and legs as reality is reshaped in its image.
- The Ultimates (2015): Initially, the series is about a team dealing with high concepts. Come issue 5, they encounter the Anti-Man, who reveals all existence has been encaged by something, only identified as "the One Who is One", capable of imprisoning the living personification of Eternity. Once the second series starts, the cosmic horror starts ramping up further, as it starts directly attacking existence itself.
- The Games We Play: The Grimm are revealed to be the creations and minions of a godlike entity who has taken an interest in Jaune. And then Jaune, or rather his soul, is revealed to be a brother-of-sorts to said entity and probably the only one who can stop him.
- The Cabin in the Woods begins as a run-off-the-mill horror/slasher story which is revealed as a setup to please the Old Gods slumbering below us. They're not cosmic, though, they just "ruled the earth before man".
- Necronomicon: Not unexpected for a film loosely based on the works of H.P. Lovecraft, but one of the segments starts out as an urban crime story with a cop in pursuit of a Serial Killer who hides out in the sewers to save her kidnapped partner. Then she's dumped inside an ancient cavern and it's revealed to all be an elaborate trap by two giant alien bats disguised as humans, and she's impregnated with their kin.
- The Midnight Meat Train begins as a Slasher-esque story about a musclebound maniac who murders people on a midnight subway train. The protagonist eventually defeats him, only to discover that the killer was part of a city-wide conspiracy to deliver human sacrifices to the indescribable terrors that live underground. He's forced to become the new Butcher and continue the cycle.
- Halo: Silentium solidifies the story of the Halo series as a Cosmic Horror Story with what the Precursors really are. Let alone the fact that they are older than the universe and are implied to have created it. Not to mention that they became the Flood.
- The Horus Heresy series is all about the secular Imperium of Mankind's discovery of the Ruinous Powers and the devastating civil war that ensues, as a direct prologue to Warhammer 40,000.
- Mistborn by Brandon Sanderson. The entire novel is spent with the protagonists struggling to overthrow the Evil Overlord, only to discover that said Evil Overlord is personally holding back a nasty Eldritch Abomination from destroying the world.
- The first three books of Venus Prime are about a young female detective who solves mysteries in space while trying to discover The Conspiracy that caused her to lose three years' worth of memories. In the fourth book, she pretty much wipes out the conspiracy. And then, suddenly, the Starfish Aliens start to show up, and the rest of the series is about her and her allies trying to prevent one faction of the aliens from attempting to re-write history so that Earth becomes more like their homeworld — which would make it uninhabitable to humans.
- In the original story of The Midnight Meat Train, if the whole "killing humans to be fed to deformed humans underground that are the true fathers of the city" shtick isn't bad enough, well, it's all for immortality granted by pleasing an Eldritch Abomination.
- The final novel of The Spirit Thief drops the bombshell revealing that the world in which the entire series has taken place is a tiny remnant of a much larger universe, and this remnant is surrounded by thousands of hungry, starving demons trying to break in and eat everything. The plot then shifts to the heroes trying to prevent the barrier between the remnant and the great nothingness from breaking.
- Journey to Chaos starts out with Eric being tossed through dimensions by a trickster god to grow a spine and provide amusement. Then it turns out that said trickster god is molding him through his adventures into a vessel for its mother, Lady Chaos, so that she may better wage war against another one of The Powers That Be, Order. This shifts the focus of the story away from worldly mercenary missions and towards more philosophical confrontations and stabbing the other guy's clerics, along with bouts of Willing Channeler that have a possibility of damaging reality.
- In Magic: The Gathering, the Eldrazi pull this in both the Zendikar block and the Shadows over Innistrad block. In Zendikar, most of the focus is on the "adventure world" with Dungeons & Dragons-style adventurers, until the Eldrazi are unleashed at the end of the second set and things get messy from there. In Shadows, the Gothic Horror plane is dealing with an epidemic of madness and mutation, and even most of the angels have fallen into darkness; "Eldritch Moon" has Emrakul, the last of the Eldrazi Titans, turn up, weld the angels together, and everything goes to hell.
- Bloodborne starts off steeped in straightforward Gothic Horror: You're a Hunter somehow implicitly empowered by the moon, trapped in a Victorian Gothic city obsessed with blood, fighting a lycanthropy plague. Then it turns out the city is made up of conflicting bands of cultists in contact with ancient, powerful alien entities whom they regard as gods. And the blood they're obsessed with is the nearest thing to a physical form one of those gods has. And the plague may well be somehow caused by the gods' attempt to spawn a half-human child. And you're probably actually trapped in another dimension dreamed into existence by those gods for the purpose of cradling that child. And the moon that empowers you is actually another Eldritch Abomination with which a contract was made to give humanity a fighting chance against the gods. And so on.
- In Persona 2, Hitler turns out to be Nyarlathotep in disguise.
- In Persona 5, it's your Mission Control Igor who turns out to be the God of Control, Yaldabaoth. Up until this point, the game had been pretty strictly Urban Fantasy.
- In Mass Effect, you're initially in pursuit of Saren, a secret agent bent on using synthetic organisms to wipe out humanity. Surprise, he's really working for the Reapers, an ancient race of machines who have wiped out all galactic civilizations several times over.
Sovereign: Rudimentary creatures of blood and flesh. You touch my mind, fumbling in ignorance, incapable of understanding.
- In Discworld Noir, the first part of the game seems like a normal mystery story, with a detective, a murder, suspects... The final part, however, involves a plan to release an Eldritch Abomination, and once it's released, finding a way to kill it.
- The Chzo Mythos does this at the midway point: The first two games were straight slasher horror stories with the single central antagonist, but starting with Trilby's Notes, the series' focus shifts to the Cosmic Horror possessing the previous games' antagonist, the titular elemental god of pain. (This is because Yahtzee was making up more story elements as he went along.)
- Earthbound tells you vaguely about Giygas throughout, but it takes the entire game to find out he's a galaxy-spanning elder god in the vein of Azathoth.
- Not the main plot, but Oracle of Tao has a bounty hunting sidequest that is relatively calm and relaxing, until you get to about the last monster, who turns out to be an Eldritch Abomination. Losing the battle against this last bounty results in a Mind Rape ending. For a Side Quest, this is still pretty heavy... and there are actually a number of these practically immortal destructive beings roaming about.
- Bravely Default is steeped in traditional fantasy tropes for most of the game, until the real Big Bad is revealed to be a world-devouring entity from beyond the cosmos.
- Halo 2 revealed that the Flood aren't just semi-sapient zombies, but are being controlled by their Gravemind, aka when a Body Horror Zombie Apocalypse acquires sentience and becomes a hyper-intelligent Eldritch Abomination Hive Mind, putting them into a good position to overrun their local galaxy and begins spreading to others nearby. The Gravemind is also able to do things like make Cortana, an AI, feel real pain, all without having to use a computer itself.
- In the original Halo: Combat Evolved, the appearance of Flood themselves shifted the focus from a war with Scary Dogmatic Aliens to something more akin to Survival Horror. We also find out that they're the ones responsible for the disappearance of the Forerunners 100,000 years ago.
- As noted in "Literature", Halo: Silentium reveals that the Flood are merely the current form of a race of Eldritch Abominations older than the universe itself.
- Halo owes this theme to its spiritual predecessor, Marathon. The game starts as a fairly straightforward alien conflict aside from a few esoteric themes. The first two games have you fighting a conventional war against alien slavers. It is hinted that there is some greater chaos towards the end of Marathon 2, but only in the context of what appears to be a mere creation myth on part of the aliens' slaves that misinterpreted a historic alien war that took place on their homeworld as being the work of the gods. Come Marathon Infinity, and the stakes of the first two games become positively trivial as you sacrifice entire timelines in a battle against this all-consuming monstrosity that is heavily implied to be a W'rkn'cacnter, as in Pathways into Darkness.
- Assassin's Creed is a perfectly normal game about an evil organisation forcing the PC to relive the genetic memories of his ancestors, tied in to an ancient-evil-conspiracy plot. After Assassin's Creed II, suddenly, Abusive Precursors arrive and the world's about to be destroyed by some sort of horrible thing.
- Then it is subverted. As it turns out, the horrors aren't cosmic. The Precursors were just animals like humans who had more senses and longer lives and better technology, the world-destroying thing was a bog-standard solar flare, and the villain's Evil Plan isn't working. Then it is double-subverted. Juno, one of the Precursors, has transcended physical existence and successfully manipulates generations of humans to free herself. She can possess humans and drive them mad. She also has a cult dedicated to her.
- Sonic the Hedgehog: It has repeatedly happened that Eggman suddenly finds himself out of his league when his schemes provoke godlike horrors, such as Perfect Chaos, Dark Gaia, and Solaris, and Sonic has to go Super to bail Earth — and Eggman — out of the mess the doctor had caused.
- Pokémon Ruby, Pokémon Sapphire, and Pokémon Emerald start off as your standard Pokémon games (battle trainers, catch Pokémon, etc.) until it's revealed Team Aqua and Team Magma want to awaken an ancient god-like Pokémon (Kyogre or Groudon, depending on which version you're playing). As can be expected, it goes far beyond expectations, resulting in either cataclysmic floods or drought that threatens to destroy all life on the planet. Naturally, it's up to the player character to save the world.
- Cyrus, the Big Bad in Pokémon Diamond and Pearl, takes this Up to Eleven by attempting to destroy and re-create the entire universe as he sees fit. He does this by imprisoning three legendary Pokémon (Azelf, Uxie, and Mesprit) in order to create an object called the "Red Chain" which he then uses to summon Dialga and Palkia (who happen to be the God of Time and God of Space respectively). Cyrus then attempts to use their power to bend reality and reshape the universe in his image. In Pokémon Platinum, this causes Giratina (a ghostly dragon-god living in an alternate dimension) to become enraged and drags Cyrus into its world (a bizarre reality where the laws of physics and so forth are far beyond human understanding. Appropriately, it's called the "Distortion World"). And, once again, it's up to the player to save the day.
- And then we have the post-game quest in Omega Ruby and Alpha Sapphire, the Updated Re-release of Pokemon Ruby And Sapphire, mentioned above. The Delta Episode revolves around an asteroid on a collision course with the Hoenn region. Hoenn's Space Center intends to stop it by using some old thing called "Link Cable" to warp it to another dimension, where hopefully it will cause no damage. However, a girl called Zinnia shows up and steals vital parts of the device explicitly to stop the Center from using it. Her reasoning is that the proper way to dispose of the asteroid is by making Rayquaza Mega Evolve and getting him to destroy it, since it's been done successfully in the past. She argues that if the scientists at the center had their way and warped the asteroid, they would save this version of the region, but would very probably send it instead to another iteration of the universe. One she explicitly says would most definitely have another Hoenn in the collision course, one where Mega Evolution never existed and would thus be defenseless against the asteroid. Yes, this is a pretty clear reference to the Hoenn from the original Ruby and Sapphire (Mega Evolution was not introduced until Pokémon X and Y, which came out right before Omega Ruby and Alpha Sapphire), and has every implication that that world would be destroyed if the Link Cable plan is executed. Long story short: The Pokémon games, as a whole, are very casually confirmed to be set all within the same multiverse. All older games that got updated, newer generation remakes, are now not simply retconned by their remakes, they exist simultaneously as different iterations of the Pokémon multiverse. And there's more: It's funny that the dimension-warping device is called a "Link Cable". Way back in the days before wireless, the only way to play Pokémon with other players was with a wire called Link Cable. Yup, it seems that now, every single copy of any single Pokémon game is, in canon, an iteration of the Pokémon universe. You've been casually leaping between universes to get that one version exclusive you needed to fill your Pokédex and totally own your cousin in a battle all these years.
- Pokémon Sun and Moon begins as another one of those stories with a young person in a new land setting out to become the champion with a villainous team... only it turns out the villainous team is highly ineffectual. Then, things really get down when a wormhole opens up in front of the protagonist, and a horrific extradimensional creature, known as an Ultra Beast, appears from it. Lusamine, the leader of the Aether Foundation, intends to open up more wormholes to bring over more of these Ultra Beasts, which eventually dominates the story. By the time the protagonist becomes the champion, Ultra Beasts are running amok on every island in Alola, and the protagonist is tasked with containing them to prevent their cataclysmic powers from destroying the world. Being the champion of Alola is small beans compared to the threat the region finds itself in.
- The Kirby series did this with Kirby's Adventure, which seemed to be a similarly cutesy followup to Kirby's Dream Land... right up until it's revealed the Star Rod you were reassembling was actually the only keeping the Nightmare Wizard, a living personification of Nightmares, trapped in the Fountain of Dreams (which was King Dedede's true goal this entire time). Notably, ever since that game, the Kirby franchise has had an Eldritch Abomination as the final boss, usually (but not always) as a plot twist, whereas King Dedede only remains a central antagonist in spinoffs and even there, it's more about Dedede trying to settle his grudge with Kirby.
- This happened to Warcraft. The series was originally about orcs and the demons they consorted with, with the demons being expanded to have been the true force behind their invasion. In Warcraft III, a "Forgotten One" was found in an underground city and fit the description of an Eldritch Abomination, but its exact place in the universe was ambiguous. In World of Warcraft, occasional appearances of the Old Gods teased the possibility that they were ultimately more of a threat than the traditional demonic Big Bad, especially since they were revealed to have been responsible for the evil of many minor villains. Finally, the World of Warcraft: Chronicle revealed that the force behind the Old Gods, the Void, is truly the ultimate threat. Not only is it a timeless element of the universe, fear of it is what drove the demons to band into a united force to begin with.
- Borderlands tried to pull this by dropping the main characters into a fight with an Eldritch Abomination. It didn't go over well, and the sequel and interquel proved willing to reference the event (often sarcastically) but focused back on the human dimension, with the Big Bad of Borderlands 2 being a perfectly mundane if staggeringly assholish humannote , and Borderlands: The Pre-Sequel! being more about his rise to power than anything else.
- Chrono Trigger's plot originally concerns itself with accidental Time Travel and the possible problems thereof, but then quickly morphs into trying to stop an Evil Sorcerer from summoning a world-destroying Eldritch Abomination, only to find out The Reveal that the sorcerer was actually trying to destroy the abomination, which is much older and much more powerful than anyone anticipated and has been manipulating the course of evolution for its benefit for over 65 million years.
- Homestuck (surprise!) becomes Hijacked By Cthulhu by [S] Jade: Wake with the revelation that the Horrorterrors do, in fact, exist... and is then more-or-less hijacked away from Cthulhu when it turns out the true villain is Lord English, a more traditional demon.
- The Order of the Stick: The first arc of the story concerns the titular Order on a dungeon crawl to stop Xykon, an evil lich and his undead and goblin minions. Then it turns out that within the lich's old lair, there was a portal to a dimension where an Eldritch Abomination with world-destroying power is imprisoned, and the rest of the story becomes a quest to stop the abomination from being released, while the lich and his minions (and several other evil forces) try to use the abomination for their own purposes.
- Worm: After spending much of the story as street-level superhero fare, with an occasional Kaiju attack, Scion is revealed to be the avatar of a Sufficiently Advanced Alien that is using Earth as a giant petri dish, with mankind as the specimens.
- The Adventure Zone: Balance starts out as a fairly typical Science Fantasy: long ago, a cabal of mad sorcerers created the Grand Relics, a bunch of Artifacts of Doom that grant superpowers at the cost of madness, and it's the protagonists' job to recollect and destroy said artifacts. As the plot progresses, it is revealed that the Relics were created to split up and neutralize the massive power source they were created from, which contains enough energy to act as a homing beacon for otherworldly entities — specifically the Hunger, an Eldritch Abomination (physically incomprehensible sans its millions of eyes and tendrils of viscous black fluid) that seeks to assimilate all worlds of the Multiverse into itself. And by collecting the Relics, our heroes have recombined the original power source and unwittingly let the Hunger loose upon the world of Faerun...
- Atop the Fourth Wall: This series starts as a comedic comic book review show. The host at first fought a Monster of the Week or Arc Villain related to the comic he had reviewed, to symbolically defeat the bad story. After the show's second anniversary, he fought a Multiversal Conqueror that was chasing an omnicidal Outer God. After that, the Outer God itself finally showed up and nearly destroyed the entire universe. Later, it's revealed that there's an entire family of such beings.
- South Park: The episode "Pinewood Derby" begins with Stan competing for the derby and his father Randy cheating to win, which catches the attention of cosmic beings who subject humanity to a morality test.
- Steven Universe features The Cluster. While the show up until that point had been raising the stakes with the looming threat of the Diamond Authority, as well as the background presence of Malachite the toxic fusion, it still had a copious amount of more relaxed breather episodes. Once the audience and the Crystal Gems are informed about this threat, it becomes the key focus for the remainder of show's second season, tying into Peridot's redemption arc. However, it's ultimately subverted as Steven manages to communicate and reason with it come the season three premiere, ending things peacefully.
- Gravity Falls starts out with two siblings exploring the weird little town they're visiting and encountering things like ghosts, gnomes, and mermen. Then the Myth Arc gets going, and Bill Cipher takes over as not just the Big Bad but the number one threat to humanity.