“No matter which god they serve, the ultimate goal of every Gnostic is the same. Summon the god they worship here. Destroy the order and dominion of our world and remake it according to the unnatural rules of the god’s tír. Whatever the outcome, to us it is pure devastation. Thus, we must stop them. Without compromise or concession, every Gnostic must be pruned. Allowing them to proliferate spells this world’s doom. We have come this close to succumbing to such threats more times than I have fingers on my hands.”
— Instructor Demitrio Aristides, Reign of the Seven Spellblades Volume 5
So you've discovered the existence of Another Dimension. Not only that, but you've likely also managed to find a way to travel into it. So far, so good: you can go to a brand new reality in order to learn more about it, study it, or maybe just to satiate your curiosity over what could've been had one thing been different.
Unfortunately, so do the pesky little invaders who travel to this dimension as well, only they have no interest in studying it, or sightseeing, no, what they wanna do is take some artifact from it, or conquer it and add it to their empire, or outright destroy it regardless of whether there's living creatures in it or not, or if they did anything to deserve it. And nine times out of ten, they'll likely threaten the stability of the dimension, too.
Now it's up to the hero to drive away the invaders and figure out a way to save the dimension from destruction!
Note that merely having a protagonist or other character who is from another universe, as in the Summon Everyman Hero, Dimensional Traveler, and/or Trapped in Another World or Reincarnate in Another World tropes, isn't enough to count: a conflict of a story has to cross the boundary between dimensions or planes of existence, or at least threaten to.
Subtrope of The Multiverse. An Alliance of Alternates can be created to deal with this if it happens too often. Or to deal with one of the most recurring instigator of conflict, the Multiversal Conqueror. Or, failing that, an Eldritch Abomination or Brown Note Being. If the conflict leads to battles through both dimensions, it can lead to Fighting Across Time and Space. If the conflict involves the potential merging of two realities, that's Merged Reality. And if it involves one reality overwriting the other, that's When Dimensions Collide. Alternatively, the conflict could end more amicably with a Save Both Worlds scenario.
A conflict that worsens badly enough can threaten to cause Apocalypse How. Though even if it doesn't get that bad, if casualties occur, then the Expendable Alternate Universe is always guaranteed to go.
See When Dimensions Collide for cases where the two worlds themselves begin to bleed into one another.
Examples:
open/close all folders
Anime & Manga
- Cross Ange: The Norma of Arzenal are Slave Mooks with the job of battling fleets of DRAGON invading from another world. Around the midpoint of the series, we learn that the DRAGONs are in fact a Human Subspecies from an alternate Earth, and are actually after the Big Bad, who split the two worlds and has been using the Norma to protect himself.
- Lyrical Nanoha:
- The backstory of the franchise prominently features the Belkan Wars (not that one), which saw the militaristic civilization of Old Belka use its advanced technology to first unify its home dimension, then to conquer neighboring dimensions, before collapsing in on itself in a catastrophic civil war when their home world became uninhabitable due to environmental damage. The fall of Old Belka was followed by the emergence of a new trans-dimensional order, which actively seeks to minimize cross-dimensional conflict through diplomacy and joint policing.
- Magical Girl Lyrical Nanoha: Precia Testarossa sends her daughter Fate into Nanoha's dimension in order to steal the Jewel Seeds, with the ultimate goal of using their power to access the lost dimension of El-Hazard, which is said to contain the knowledge of how to resurrect her real daughter Alicia, of whom Fate is merely an expendable clone.
- Semelparous: Two parallel Earths exist across a Void Between the Worlds. One was conquered long ago by the Mures that lived in the void, who use the humans of that world to create kaiju which they then send to attack "our" Earth in a Forever War with Mure dissidents, who interbred with humans to create the Bulwarks that intercept the kaiju in the void.
- Towards the end of Season 2 of Sonic X, it's revealed that our dimension and Sonic's dimension were once one and the same before diverging; Sonic's extended stay in our dimension is causing the two to begin merging again, which would eventually result in time freezing forever. As a result, Sonic and friends are forced to return to their own time.
- Vividred Operation: Seven years after the creation of the Incarnate Engine, a revolutionary power plant that powers 90% of Earth, monsters called the Alone begin appearing from another dimension to try and destroy the Engine. Its creator saw this coming, and created the Vivid System to defend the Engine.
- Yu-Gi-Oh! ARC-V: One of the earliest big Reveals of the series was the existence of four dimensions based on Extra Deck summoning methods: Fusion, Synchro, Xyz, and Standard (where the show starts and uses all methods). By the start of the series Fusion has already invaded and almost completely subjugated the Xyz Dimension, turning it into a war-torn wasteland, LDS of Standard is secretly preparing for an invasion, and there are Fusion spies in Synchro. At first it appears that the reason is Fantastic Racism (aka Fusion users wanting to prove they are superior) while later in the show some high-ranking members reveal that the goal of the Professor (who started the invasion) is to unite the four dimensions and create a Utopia. Only towards the very end it's revealed that the four dimensions were originally one, and the Professor seeks to re-fuse them in order to bring his daughter Back from the Dead, who performed a Heroic Sacrifice in order to split them in order to seal the Greater-Scope Villain.
Comic Books
- The Avengers (Jonathan Hickman): The Incursions are perhaps the most devastating event to Marvel Multiverse to date. One Earth from one universe crosses over to crash into another. While two planets from different universes might not seem as devastating in comparison to other events, but that's until it's revealed that both universes will be destroyed upon collision, and the only way to stop it is by destroying one Earth to save both universes, or by using something like the Infinity Gauntlet to move the Earth so it doesn't crash into another. Unfortunately in the end, everything dies. The Prime Universe (Earth 616) and the Ultimate Universe (Earth 1610) are the last universes to collide, marking the end of all creation. But fortunately enough, there's still hope, and then everything lives..
- Crisis on Infinite Earths: When the Monitor and the Anti-Monitor learned of each others' existence, they engaged in a battle between them, the Monitor attacking from the positive matter universe, and the Anti-Monitor from the anti-matter universe. They were initially at a stalemate, until a scientist's experiment made the Anti-Monitor realize he could gain more power (and diminish the Monitor's) by using a wave of anti-matter to destroy positive matter universes.
- Fantastic Four (1961): In issues #251–256, the Fantastic Four take a trip into the Negative Zone, thanks to a trans-dimensional tunnel that Reed Richards built. While they have some adventures there, including the problem of getting back to their rightful dimension, the vicious tyrant Annihilus crosses over into New York City, where he begins a reign of terror.
- Forever Evil (2013): The Outsider (a counterpart of Alfred Pennyworth from Earth-3) takes a skull-shaped box from Pandora and opens up a portal to his native dimension, Earth-3, allowing the Syndicate of Crime to step into Prime Earth. The Syndicate are villainous versions of the Justice League; they defeat their Prime Earth counterparts, locking them up into Firestorm's fusion matrix, and make their moves to dominate this new dimension. Without the Justice League, the only survivors of the team, Batman and Catwoman, make an uneasy alliance with the major antagonists of the Leaguers (e.g., Lex Luthor, Captain Cold, Sinestro, etc.) and other villains in order to take back their world.
- Star Trek: Debt of Honor: The so-called "critters" are a Horde of Alien Locusts that for decades has been attacking ships in the border region between the Federation, the Klingon Empire, and the Romulan Star Empire, striking then withdrawing into Another Dimension. This ultimately forces the top captain of each Space Navy—James T. Kirk, Dahar Master Kor, and Commander T'Cel—to team up to lure the critters into their counterstrike. In the end, T'Cel leaves in her ship to enter the critters' dimension and defeat them permanently, and is never seen again.
Fan Works
- Boldores and Boomsticks: When the Ultra Wormholes connect Remnant and the Pokémon world, Salem sends her Grimm between dimensions to attack Earth whenever possible so the two worlds won't communicate and join forces against her.
- Digital Storage Solutions: Digimon data accidentally enters the Pokemon universe's data storage systems, leading to the discovery of other universes by a villain team, then said villains fleeing their home universe for universes unknown, until they reappear in the third book, making trouble that the heroes are rushing to solve.
- The Dresden Fillies: Technically, the ponies' My Little Pony: Friendship Is Magic world and the human The Dresden Files world share the same universe, with just a magical interworld zone separating them. In the third story, Twilight Sparkle, a pony, causes conflict in the human world just by travelling there and not knowing how to interact, then a monster from the interworld zone enters the human world because it followed her trail.
- Dungeon Keeper Ami: Ami is a hero from the Sailor Moon setting who accidentally lands in Dungeon Keeper's Adushul setting, and still manages to disrupt the plans of her enemies from her home universe:
- Those enemies make plans to cross dimensions and attack her again, and have managed to land in what appears to be Adushul's underworld, where they can then be Thinking Up Portals to attack Ami with.
- Adushul's God of Good collective would like it if Ami didn't mess with her old enemies while in their world, because it might mean the Adushul God of Evil collective might learn that there's easier, less well-protected worlds out beyond the Void Between the Worlds to conquer.
- Five Score, Divided by Four: The war on Discord concludes when he sends a massive chunk of the population to be reborn on Earth in a separate dimension. 25 years later, after relearning their roots, the Equestrians amass as many of their ranks as they can to march back through the portal and take the fight back home.
- The Mountain and the Wolf: Wulfrik the Wanderer's longship is enchanted to sail through the Warp and emerge in realspace close to his target. This makes it an Obvious Crossover Method for him to enter other fictional universes (including, it's implied, Harry Potter and Le Donjon de Naheulbeuk), and the story starts when he appears in the Game of Thrones version of Westeros to butcher Gregor Clegane, taking the place of Oberyn Martell during their climactic fight in "The Mountain and the Viper". He then sporadically shows up to kill other notable figures in Westeros in preparation for a Chaos invasion, but because he does this shortly before the characters died in the series, the plot doesn't deviate much from the series until the very end, when the invasion starts in earnest.
- Scootertrix Is For Adults: The Princess Celestia of Scootertrix the Abridged finds a portal to the universe of Friendship Is for Adults—and she sends three spies into the other universe in a misguided attempt to find and punish someone who's been sending her anonymous hate-mail for weeks. Meanwhile, the Celestia from Friendship Is for Adults also finds the portal and realizes her universe has been infiltrated, so she sends three spies of her own to counter-infiltrate the Scootertrix universe. Fortunately, both sets of spies just get into mistaken identity shenanigans rather than causing an interdimensional incident. In the spinoff series Royal Correspondence, both universes' versions of Princess Luna write to each other to resolve the lingering diplomatic tension and wind up becoming penpals. But ten episodes in, a fourth-dimension being shows up in the FIFA universe to chew the Princesses out over the recent portal incident. According to him, crossover between universe threatens the stability of the entire multiverse. He reluctantly allows Luna to continue writing to her Scootertrix counterpart, on the condition that they cut off all physical travel between universes.
Film — Animated
- Justice League: Crisis on Two Earths: When Owlman becomes aware of the multiverse, he comes to the conclusion that new universes are created every time a sentient being has to make a decision (there is some evidence that undermines this theory, but Owlman is a Straw Nihilist). Based on this belief, Owlman concludes that the only thing anyone can do that would actually matter is destroy all life throughout the multiverse.
- Pokémon: Giratina and the Sky Warrior: The villain is trying to take the powers of Giratina, the ruler of the Reverse World, for himself. Near the end of the movie, he gets the power and then conflict turns into him recklessly breaking things in the Reverse World, which leads to disasters in the "normal" world as well like a glacier moving.
- Rock & Rule: Big Bad Mok succeeds in bringing forth a demon from another dimension during a concert at the Ohmtown power plant. The towering Eldritch Abomination devours some of the audience before turning its attention to lovely songstress Angel. The heroes manage to reverse the process, and send the monster back from whence it came.
Film — Live-Action
- Cool World: The Vamp Holli Would succeeds in getting her hands on the Spike, which is acting as a cork that keeps the Toon Town of Cool World separate from the real world. She removes it, which immediately causes a flood of toony characters to spill into Las Vegas. This causes regular people (Noids) to transform into cartoons (Doodles), and develop Toon Physics instead of Newtonian physics. With Detective Harris dead, it's up to artist Jack Deebs to reclaim the Spike, and set it back in its rightful place.
- Marvel Cinematic Universe:
- Doctor Strange: The Ancient One founded Kamar-Taj to protect Earth from extra dimensional threats. The Mirror Dimension is used for training and combat. The Big Bad Dormammu lives in the Dark Dimension, and the Zealots draw power from the Dark Dimension and are stronger in the Mirror Dimension. The Ancient One also draws power from the Dark Dimension. Doctor Strange learns how to use the mirror dimension to fight the Zealots and later has to meet Dormammu in the Dark Dimension. Dormammu wants to fight Strange but Strange has other plans.
- Spider-Man: Far From Home: Subverted. Mysterio claims that the Elementals destroyed his home universe's version of Earth and then followed him to this one, which he calls Earth-616. He's lying: he's from this Earth (which was stated to be Earth-199999 initially, though retconned to be Earth-616 in Doctor Strange in the Multiverse of Madness), and the Elementals are holograms he himself created using Stark Industries Attack Drone technology.
- Doctor Strange in the Multiverse of Madness: Doctor Strange meets a teenage girl named America Chavez who has the power to open portals to other dimensions. After being thrown into another world, Strange and Chavez must travel the Multiverse together to confront an old friend-turned-adversary and foil a dangerous plot that may threaten all realities.
- The One (2001): Alternate Selves all share the same pool of life energy, so an interdimensional criminal sets off to kill all 124 of his alternates so he can absorb their strength and gain godlike power. It also threatens a Reality-Breaking Paradox that could destroy one or more universes.
- Pacific Rim: Earth comes under attack by kaiju entering our world through a dimensional rift at the bottom of the Pacific Ocean. The kaiju are discovered to be living weapons designed to exterminate humanity on behalf of the denizens of an alternate universe so they can take Earth for themselves.
Literature
- Arifureta: From Commonplace to World's Strongest: The Big Bad, the god Ehitorujue, is ultimately revealed to be planning to abandon the Standard Japanese Fantasy Setting he kidnapped Hajime's class into, and invade Earth to toy with and trash it just like he did the fantasy world.
- The Beyond Reality series is pretty much made of this, as the conflict in every single book and short story involves some sort of interdimensional anomaly or incursion. This varies from more conventional invasions between universes from advanced polities to attacks by Gods or eldritch horrors and everything in-between.
- In Philip K. Dick's novel The Crack In Space, a malfunction in an experimental warp drive instead opens a rift to an "alter-Earth" in another universe, where Homo sapiens either never evolved, or died from competition with other early hominid species. The local sapient life are instead Homo erectus (aka "Peking man", or "Pekes" as they're soon nicknamed), who are less technologically advanced. As the Earth is suffering from severe overpopulation, those in power immediately decide to colonize alter-Earth so their excess population can settle there. However, one of the initial colonists sets himself up as a god to the Pekes, and leads them in sabotaging the colonization efforts and ultimately counter-invading the Earth.
- The backstory of Endo and Kobayashi Live!: The Latest on Tsundere Villainess Lieselotte involves this, including why the inner fourth wall disappeared in Endo and Kobayashi's "MagiKoi" commenting sessions in the first place. Because the MagiKoi Universe is a separate (but equally real) dimension. That dimension has a Creation Myth similar to the Abrahamic one, with the exception that The Maker divided into a God Couple upon descending their equivalent on Earth, the male Kuon and the female Lirenna. And then Kuon falls in love with Eve, one of the first female humanoids, and murders Eve's husband Adam because of it. Lirenna was scorned, corrupted into the Witch of Yore, and banished Kuon out of their Earth. Kuon, however, eventually stumbles into our Earth, when he took over a person and bankrolled MagiKoi, a Romance Game based on the current situation in his original world, with a secret "God Mode" where he can manipulate the narrative and causes Eve's current reincarnation Fiene to travel to Earth, where Kuon prepares her with a body—that of the sister of the titular Kobayashi.
- The Executioner and Her Way of Life: Title character Menou is an assassin in a Standard Japanese Fantasy Setting whose job is to kill Japanese people that Reincarnate in Another World because of the damage they keep causing to her world. Unfortunately, her latest target turns out to have Resurrective Immortality as her New Life in Another World Bonus, so Menou is stuck traveling with her and keeping her out of trouble while she figures out how to kill her permanently.
- The Expanse: It turns out that the Portal Network that has opened up between Caliban's War and Abaddon's Gate works by transferring matter to and from another universe and exploiting massive amounts of energy produced by this process. That other universe also turns out be a home to incredibly alien beings that... don't like having energy from their universe stolen. They are the ones responsible for wiping out the civilization that made the protomolecule and the portal network, and presently they make occasional human spaceships vanish during dimensional transfers. Humans have adapted to this by tightly regulating the interdimensional traffic to avoid exceeding the network's "bandwidth", but then in Tiamat's Wrath, the megalomaniacal Winston Duarte gets the bright idea to play carrot-and-stick with these beings.
- Reign of the Seven Spellblades: "Our" world periodically passes close enough to other worlds of The Multiverse, called tírs in the lore of the series, for beings to migrate between them. Some migrations are innocuous—many magical creatures of the world originated on other tírs—but others are basically Alien Invasions, especially those instigated by the tír's god, who sees the protagonists' godless world as an easy target, and both invade overtly to reshape the world in their image, and establish cults to their worship, called Gnostics. A primary purpose of Kimberly Magic Academy is to train Gnostic Hunters to combat such incursions—though even by that standard, mages tend to take it to extremes and cause as many problems as they solve, and some mages try to perform academic research on other tírs, which can lead to either great breakthroughs or disaster with seemingly no middle ground.
- Torchwood (BBC Books): In The House That Jack Built, Jack stumbles into a "potential dimension", filled with lifeforms who feed on temporal paradoxes. They're rather interested in a house called Jackson Leaves, due to Jack damaging two timelines around it, and if it hadn't been for Jack going back in time and ensuring that his past self never bought the house at all, they would have successfully broken their way into the main dimension and destroyed it within minutes.
Live-Action TV
- The Call of Warr: Vid is obsessed with trying to merge his dimension with the more powerful and divine dimension he's been speaking to lately — that is, our dimension, as he was speaking to the viewers calling in. This threatened to rip reality apart, and he was only stopped just moments from completing his insane goal by the ghosts of the characters who died during the show giving magic-user Ashes the strength to defeat him.
- Fringe: Season 2 reveals that the Myth Arc was kickstarted by Walter in the 1980s; the native universe's Peter Bishop, Walter's son, died as a result of an illness, and after Walter managed to develop a cure, he abducted Peter from an Alternate Universe; this has since resulted in the degradation of reality on the other side, and a secret war being carried out by agents from the alternate reality that the majority of people are ignorant of.
- The titular character in Kamen Rider Decade travels between alternate Kamen Rider universes, saving the day there every time. However, it is later revealed the evil organization Dai Shocker is taking over several of these universes, which cumulates in The Movie, where they launch a massive attack against the multiverse. Fortunately, the Kamen Riders from these universes team up to defeat Dai Shocker.
- Kikai Sentai Zenkaiger involves villains from Kikaitopia freezing other universes, including those of the previous 44 Super Sentai teams and a world where they all co-exist, Supersentaitopia. Some worlds are freed by destroying the Monster of the Week. The last world standing becomes known as Zenkaitopia.
- Loki (2021): The entire premise of the series is that the MCU is the "Sacred Timeline" and any deviation from the sacred timeline that would caused either someone to deviate out of that timeline (called "Variants") would lead to that timeline being decimated (or "pruned") and the person that caused the deviation to be captured and worked for the TVA or being sent to the Void to die. The season 1 finale revealed that the real purpose of the TVA, founded by "He Who Remains"—who became Kang the Conqueror in other timelines—is to prevent another multiversal war caused by Kang and his variants by erasing all other possible timelines from existence.
- Star Trek:
- Star Trek: The Next Generation: "Schisms": A sensor modification attracts the attention of an alien species that lives in subspace, which begins abducting Enterprise crew members to experiment on them, while opening a hole into their own spacetime from within the ship's cargo bay.
- Star Trek: Voyager: "Scorpion": The Borg attempted to invade the alternate dimension "fluidic space" in order to assimilate its inhabitants, chiefly its dominant civilization which they dubbed "Species 8472". This race did not take kindly to the attempt, crushed it with superior firepower, and then counterattacked into normal space with the aim of exterminating the entire Borg Collective. When Captain Janeway inexplicably decides to side with the Borg, 8472 declares war on the Federation, too.
- One of the factions of the Temporal Wars introduced in Star Trek: Enterprise is from a trans-dimensional realm with plans to conquer the Milky Way. After learning that The Federation will defeat them, they manipulate the Xindi to try to destroy Earth, which would prevent the Federation from forming.
- Season 3 of Star Trek: Discovery then reveals that one agent of the Temporal Wars infiltrated the Prime Universe from the Kelvin Universe.
- Twin Peaks: The murder of small-town homecoming queen Laura Palmer seems like a crime of ordinary passion on the surface, until the investigation leads to the extradimensional Black Lodge, a gateway to a surreal world populated with bizarre characters and creatures. An escapee from the Black Lodge called Killer BOB turns out to be Laura's murderer.
Tabletop Games
- The Delver's Guide to Beast World is set after the attempted invasion of a World of Funny Animals by the human survivors of a dying alternate universe where the laws of physics were breaking down. The war ended with the integration of most Broken World survivors into the Beast World's countries, but in the aftermath a mega-Dungeon somehow managed to build itself under the the Beast World and has started to emerge on the surface.
- Dungeons & Dragons:
- In the "Great Wheel" cosmology shared by most campaign settings, the two planes of the Nine Hells of Baator (inhabited by devils) and the Infinite Layers of the Abyss (demons) are locked in a Forever War called the Blood War.
- Planescape:
- The Harmonium are an army dedicated to the cause of law and good, predominantly law, and have already conquered their home plane and eliminated all chaotic creatures. They then attempted to conquer the rest of the multiverse, starting with Sigil, but failed. Instead they settled for becoming one of the dozen-odd factions vying for influence in Sigil and acting as the interplanar city's police.
- The premise of the 5E adventure module Turn of Fortune's Wheel is that something has upset the balance of the multiverse, one of the more visible effects on the players being a form of Resurrective Immortality where they get replaced with an alternate version of themselves when killed.
- GURPS: Alternate Earths and Infinite Worlds: The background is a Space Cold War between the three universes that have discovered interdimensional travel. Homeline, the first universe to discover the secret and more or less a more technologically advanced version of the real world. Centrum, an Orwellian socialist police state that is trying to influence other timelines to be more like themselves. And Reich-5.
- Magic: The Gathering: The storyline for March of the Machine had New Phyrexia invade the entirety of The Multiverse using the Realmbreaker; while they were pushed back, The Masquerade surrounding the existence of other planes, which had been maintained by Planeswalkers for millennia, was irreparably shattered, and anyone can go through the Omenpaths the Realmbreaker left behind.
- Pathfinder:
- According to the book Concordance of Rivals, Pharasma, goddess of the dead, is the Sole Survivor of the previous iteration of The Multiverse, and crafted a shell around the world to shield it from the attentions of Eldritch Abominations called "Those Who Remain". Pharasma and the other denizens of the Boneyard are also constantly at war with the daemons of the plane of Abaddon, who actively oppose the cycle of reincarnation and often raid the River of Souls to carry the recently deceased back to Abaddon to fuel their efforts.
- One of the consequences of the death of the god Aroden in 4606 AR was the opening of the Worldwound, a dimensional breach to the Abyss that allowed an ongoing invasion by The Legions of Hell. In response, the nations of Avistan marshalled a series of crusades to hold the demons back, starting a Forever War. The Wrath of the Righteous Adventure Path deals with the final, canonically successful Fifth Crusade to close the Worldwound and end the invasion for good.
- Warhammer 40,000: One of the major factional groups is the Ruinous Powers of Chaos, who exist primarily in the alternate reality commonly called the Warp, through which all Faster-Than-Light Travel must somehow pass. The fournote Chaos Gods and their innumerable servants constantly war with both each other and the denizens of normal space, opposed mainly by the Imperium of Man and the eldar (the other factions will fight back if attacked, but the humans and the aeldarii are the only ones actively trying to defeat Chaos permanently).
- The Ruinous Powers also exist in Warhammer: Age of Sigmar, with the added benefit of being confirmed to exist across multiple realities, as Archaon filled in the time between destroying the Old World and invading the Mortal Realms by invading every other reality he could find and destroying them. There are officially five of them in Age of Sigmar, with the Great Horned Rat having been raised to a full member of the pantheon as he leads his forces from their own pocket dimension.
Video Games
- 5D Chess With Multiverse Time Travel: In some of the variants, both sides' armies begin in entirely separate timelines. This essentially turns the game into a war between timelines.
- Several of the products from Elephant Games are confirmed to take place in a Shared Universe, and there are a number of installments which pit the heroes against characters from parallel dimensions which resemble their own. Mystery Trackers, Detectives United, Grim Tales, Haunted Hotel, and Paranormal Files have all dealt with enemies from these alternate dimensions crossing into theirs in order to steal valuable Plot Coupons or kidnap people. The members of Detectives United also dealt with the reverse problem — someone from their own dimension trying to channel power from other dimensions.
- Final Fantasy XIV:
- In the "Shadows of the First" storyline, Ardbert leads his "Warriors of Darkness" from the First, an alternate dimension, to the Source in hopes of triggering a Calamity. Ardbert and his friends believe that having their world destroyed and subsumed into the Source is better than the Fate Worse than Death that awaits if the Flood of Light is allowed to reach its completion. The Scions fight against Ardbert's team to prevent the catestrophic damage that would cause.
- In the post-Endwalker storyline, Golbez, a sovereign of the void, seeks to tear open a hole between his world and the Source so the void's denizens can sate their Horror Hunger via the Source's bountiful aether and die a proper death. But given the chaos that such an enormous voidsent incursion would cause, the heroes fight to stop Golbez's plans and defend their world.
- Grim Dawn has the unfortunate inhabitants of Cairn caught in the crossfire of one such conflict between Aetherials (incorporeal invaders from the Aetheric realm) and Cthonians (eldritch horrors from the Void), as the former's invasion leads to cultists immediately summoning the latter. Both fight each other over what to do with humanity, with Aetherials wishing to use them for Demonic Possession and Cthonians wishing to drain them of all blood to reassemble Cthon itself from it; humans themselves are just trying to survive in the ensuing post-apocalypse, with little (but existent) hope to reclaim their world one day.
- Gunslinger Stratos: In 2115, two Alternate Timelines begin merging, which would ultimately destroy both. To prevent this, each side launches a military operation to travel back in time and destroy the other dimension first.
- Mortal Kombat 1: It's eventually revealed halfway through the plot that the mysterious benefactor that turned Shang Tsung and Quan Chi From Nobody to Nightmare is Shang Tsung from an alternate timeline where he won the battle for Kronika's hourglass, using a Kronika-like disguise invading Liu Kang's New Era. This leads to Liu Kang searching other timelines for other Titans of Time, eventually finding Titan versions of Kitana, Raiden and Kung Lao. The ending has the four of them searching not only for more Titan allies, but also forming an Alliance of Alternates in order to take down Titan Shang Tsung's own one and himself for good.
- Pathfinder: Wrath of the Righteous: One of the consequences of the death of the god Aroden in 4606 AR was the opening of the Worldwound, a dimensional breach to the Abyss that allowed an ongoing invasion by The Legions of Hell. In response, the nations of Avistan marshalled a series of crusades to hold the demons back, starting a Forever War. The game's campaign deals with the final Fifth Crusade to close the Worldwound and end the invasion for good.
- In Shin Megami Tensei, a recurring element is the threat of demons crossing over from their native realm into our world (sometimes being summoned by devoted followers or unwitting civilians using something they don't understand, like the Demon Summoning App, other times the forces of Order And Chaos just breaking through the dimensional barrier after some threshold has been passed). While a few of them might have had some influence on the human world, being the In-Universe source of various myths and religions, their physical arrival en masse is often the inciting incident in the narrative (at least when the story isn't set in the post-apocalypse after the demons invaded). The stories often have debates about whether or not it's better to side with one of the invading factions rather than drive them off, as some believe that they might be able to fix whatever mess of a world humanity had made for itself.
- In Sonic Rush, Eggman stealing the Sol Emeralds from Blaze's dimension and misusing them in Sonic's dimension is causing the two dimensions to merge together; if allowed to continue, it will cause catastrophic, irreversible damage to both.
- In Stellaris, the Extradimensional Invaders (Unbidden, Aberrant, and Vehement) are three different factions of invaders from another dimension. If they appear as an/the endgame crisis, they'll try to feed on the energy of every inhabited planet.
- Ever since Super Robot Wars EX, the Super Robot Wars franchise has had invasions from alternate universes requiring a heaping amount of Hot-Blooded Justice to quell these attacks. Sometimes they’re series-based like Byston Well or Cephiro or they can be Original Generation places like La Gias or the Shadow Mirror universe.
Web Original
- Fallen Kingdom (CaptainSparklez): An army of Pigmen from the Nether invade the royal family's kingdom in the Overworld. In the finale, the King and Prince go into the End, where the King tames the Ender Dragon and rides it back into the battle in the Overworld.
- SCP Foundation:
- SCP-1322
is a heavily guarded portal to an Alternate Universe. Contact with the locals was friendly until the Foundation gave them a flu vaccine that somehow caused a global Sterility Plague, provoking the locals to launch a Lensman Arms Race just to get revenge on the Foundation's world.
- SCP-8457: "That time I, a Foundation Agent, was abducted into another world at war with mine.": Praying-mantis-like beings from another universe are abducting humans as part of a war with the human universe. Humans can use world-hopping inventions to counter-attack.
- SCP-1322
Webcomics
- Jupiter-Men: Earth (known in the ancient past as Prime) was once inhabited by the Primari, who left Prime to obtain fantastic powers in other dimensions. However, these ex-Primari lost their connection to Prime in time, leading the two most powerful dimensions, Magi and Mechi, to go to war to claim dominion over Prime and its energies. The resulting conflict nearly destroyed Prime until Mother Nature, a powerful Primari, developed the Star Seed to safely harness Prime's energies, free the Primari that the Magi and Mechi enslaved to open portals, and force the Magi and Mechi back into their dimensions. In the present, Mother Nature's descendants continue to use the Star Seed to defeat the starstruck, monsters born of creatures corrupted by cosmic energy, and keep Prime safe from extradimensional visitors who attempt to cross over to Prime illegally.
- Strange Tales of the DA Multiverse: An evil version of Captain Evening called Lord Dies assembles a crew of supervillains from different universes in order to hunt down and kill his heroic counterparts in other universes.
Western Animation
- Amphibia involves three girls from Earth — Anne Boonchuy, Sasha Waybright, and Marcy Wu — being teleported to the titular dimension as a result of opening the music box, not only separating them, but draining the box of its magic, forcing the girls to survive in Amphibia until they can figure out a way to go home. Later, it turns out that the music box, called the Calamity Box, was once used in Newtopia by King Andrias' ancestors to ransack the multiverse for resources, until Leaf, the Plantar family's ancestor, stole the music box and ran away to hide it on Earth, hoping to stop Newtopia's conquering ways once and for all when she received a vision of Amphibia's destruction as a result of continuing them.
- Chaotic: In one episode, Underworlders appeared in the Real World from the land of Chaotic by means of an inter-dimensional portal, and attempt to take it over. It was actually All Just a Dream, as Kaz was really just dozing off while attempting to cram for an upcoming test.
- Invincible (2021): The main plot of "Here Goes Nothing" deals with Earth getting repeatedly invaded over several days by aliens from another dimension, with casualties of both civilians and supers gradually mounting as the Flaxans learn from each attempt, since time moves much faster in their home universe. Omni-Man ultimately wipes out their final attack himself after Invincible and the Teen Team are overwhelmed, before charging into their portal and personally bombing them back to the Stone Age.
- Jonny Quest: The Real Adventures: "Otherspace": Using tech derived from theories of Dr. Quest, the military opens a portal to another world and sends in a probe. The denizens of the other dimension prove hostile, trying to convert Earth to their environment. Dr. Quest is able to convert a force field he invented to contain the nuclear blast of the military installation's self destruct to prevent it from damaging the surrounding area, and channelling the blast back through the portal, taking out the hostile force. Quest also creates a personal force field powerful and compact enough to allow him to survive unscathed at the heart of a nuclear blast.
- In the Miraculous Ladybug special "Paris: Tales of Shadybug and Claw Noir", a heroic version of Gabriel Agreste from a darker universe visits Ladybug's universe, hoping for proof that his universe is an aberration. Unfortunately, he is followed by Shadybug and Claw Noir, the champions of his universe, who are filled with envy that their counterparts have better lives, and thus try to kill and replace Ladybug and Cat Noir.
- The plot of Sonic Prime kicks off when Sonic accidentally destroys the Paradox Prism, resulting in the creation of the "Shatterverse", a network of alternate universes populated by doppelgangers of Sonic's friends. The main conflict kicks off when the Chaos Council, the evil Alliance of Alternates that rules one of the Shatterspaces, learns of the Shatterverse and decides to conquer it. Later on, a secondary conflict begins when Nine, one of Tails' duplicates, realises that a) Sonic only sees him as a Replacement Goldfish for Tails and not an individual in his own right, and b) if the Paradox Prism is repaired and the Shatterverse undone, he will cease to exist.
- Spider-Man: The Animated Series: This is the premise of the last arc, "Spider-Wars". Spider-Carnage, a clone from an alternate counterpart of Spider-Man, jumps dimensions in order to gather the necessary resources to build a "time dilation machine" and destroy the universes. The Spider-Man of the main reality is recruited by extradimensional beings Madame Web and Beyonder, along with other counterparts, to stop Spider-Carnage.
- What If…? (2021): The premise of the series involves Uatu looking over various alternate universes. For the most part, he does his best not to get involved with the people of these universes for this exact reason. When Infinity Ultron gains heightened awareness that allows him to see Uatu though and realizes there are universes beyond his own, Uatu realizes how much of a multiversal threat Infinity Ultron poses which prompts him to break his oath.
- X-Men: Evolution: In "Shadow Dance", Forge conducts a test on Nightcrawler and discovers the latter's teleportation power works by having him quickly move across another dimension before reappearing in his desired destination. Unfortunately, the experiment ends up generating a rift between worlds, enabling the other dimension's inhabitants, a race of feral, raptor-like demons, to cross over and wreak havoc on the heroes' world.
