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- At one point in the Berserk manga's Millennium Falcon arc, Schierke has to go inside Guts' mind using Astral Projection to snap him out of the influence of his inner beast the first time he uses the Berserker Armor.
- Black★Rock Shooter has the titular "otherselves" as apparently "censor" mechanisms that remove pain and frustration from their human selves. The problem is that the effect "bleeds" out and the titular Black Rock Shooter is removing what she considers to be pain and suffering in other people's heads. The finale is Mato; Black Rock Shooter's human self; taking control of her Black Rock Shooter function, splitting from, and then beating down her Knight Templar tendencies which takes the form of Insane Black Rock Shooter.
- The Manga adaptation of Breath of Fire IV has Ryu and Fou-Lu merge into Infini and then mentally duke it out for control of the creature. This is a Third-Option Adaptation from the game, where Ryu either resists the merge and fights Fou-Lu's Tryant dragon with his allies, or he accepts the merge and Fou-Lu takes control of Infini, easily wipes out Ryu's friends, and proceeds to destroy the world.
- Fubuki Shirou of Inazuma Eleven had a bad case of this in season two. While earlier on he was fairly stable maintaining his personalities, slowly he loses control of himself to his other personality, and at some point Atsuya successfully took total control of Shirou. But after he merged with Atsuya, this no longer became a problem.
- Mahou Sensei Negima! has Negi fighting Evangeline (or at least a being created from his memories of her) inside his own head as part of his test for learning Black Magic.
- Done backwards in Martian Successor Nadesico when Akito engages in a virtual battle with the ship's computer to delete its memories. In this case deleting the computer's memories was the heroic thing to do, but the computer wasn't aware of this and fought to protect itself. Both Akito and the computer chose to virtually represent themselves as Gekigangar III, the titular giant robot from Nadesico's Show Within a Show, combining this trope with Fearful Symmetry.
- Chapter 493 has Naruto vs. the embodiment of his hatred at the Waterfall of Truth. The scenery doesn't change, however, indicating that it's more of a hallucination than going to the center of his mind.
- Shortly after that, Naruto fights the Kyuubi (Nine-Tails) within his mind. Yes that Kyuubi. The one that he has had no control over and been terrified of most of the series.
- It also turns out to be a subversion. It may have been a battle in Naruto's mind, but that didn't make it any less real. Naruto using named attacks instead of unnamed also lends credence that he could do almost anything he did in the battle in the real world.
- Crops up in Paranoia Agent; Or is it a Lotus-Eater Machine?
- Puella Magi Madoka Magica the Movie: Rebellion has the cast fight inside Homura's soul gem, to stop her transformation into a witch.
- Happens between brother and sister Masamune and Tsubaki Nakatsukasa in Soul Eater. The conflict between the two souls (Masamune being able to possess Tsubaki, which she allowed in order to confront him) is shown as a physical battle between the two, each using their own weapon forms. Souls get Mental Worlds elsewhere in the series, but this is the only actual battle so far. Curiously, Black Star's attempt at mastering the form possessed (and corrupted) by Masamune ultimately involved not a similar fight but a conversation.
- Ranmaru from Tokko has to do this after an encounter with Taishi results in him losing control of his phantom.
- In Weiß Kreuz Gluhen, Berger draws Crawford into his own psychic mindscape to fight him. Crawford, however, manages to turn it around on Berger and pull both of them into the center of his own mind - and unlike in Berger's, in Crawford's mind, they aren't alone.
- In The World God Only Knows, Keima Katsuragi has some of the most extreme (and funny) wars in his head over various video game related subjects. One involved a enormous space war complete with Mobile Suit Gundam and Star Wars references, fought by armies of himself. Though it's probably his imagination.
- Incredible Hulk: During Paul Jenkins' run, one of Bruce Banner's Hulk personalities, the 'Beast', a near-mindless monster, threatens to take over completely, so Bruce journeys into his mind and recruits the three main Hulks - Savage Hulk, Joe Fixit, and the Professor - to defeat it on his/their home turf.
- Star Wars: Legacy features a power struggle of two Sith Lords in each other's minds. Lightsaber fights are blank compared to what they can achieve in that state.
- In X-Men, the only way to save a person infected by the Brood is to kill the parasite's mind; unless you are a very good telepath you won't be able to save yourself. Heroic Resolve won't solve the matter—it is necessary for the help to be able to arrive in time in the first place. (Or, you need to be Wolverine. Or Rogue with Wolverine nearby.)
- The Avengers played with this one in the 2001 annual, involving Hank Pym's separate personalities (Goliath, the cold unfeeling reason, and Yellowjacket, the impulsive showoff) who hated each other's guts getting dumped into a psychic landscape that was supposed to represent the original's mind after they were physically separated into two people in the real world. Initially, they started fighting for control, even trying to force Janet (who was back together with him at the time) to choose which one would live. Only after they both accepted the previously ignored third aspect (the human combination of both) were they put back together, keeping him from dying.
- The final battle of Scott Pilgrim is like this. A part of Ramona still wants to be with Gideon. All the other parts want to beat the crap out of him, though.
- The Reboot version of the Legion of Super Heroes had a memorable one, when Saturn Girl enters Shrinking Violet's mind to help her free herself of the control of the cursed Emerald Eye of Ekron, which is using her body to attack the rest of the team.
- In a 2002 comic book, Donald has to fight the Beagle Boys in Uncle Scrooge's dreams before the Boys find out the combination to Scrooge's vault.
- Issue 8 of Flash Gordon Zeitgeist has this with Hans Zarkov.
- X-23 is drawn into one in The Killing Dream. A demon attempting to recruit Laura to his service tells her that as a clone she has no soul. When she refuses and denies this accusation he fatally wounds Julian to force her hand, offering to spare him if she accepts a place as leader of his armies. Laura once again denies him, so the demon offers her another option: Prove him wrong. When she agrees to this the demon drags her into a hellish landscape within her own mind, presenting her with images of all the death she has caused and will yet cause to break her will. However Laura encounters her inner self, who reveals that she wasn't born an emotionless killing machine but that it took the conscious effort of the Facility to break her. This revelation, and the memory she is shown of defying her orders to spare the young son of Martin Sutter (actually the son of one of her creators, Zander Rice, through an affair with Sutter's wife) when sent to kill the entire Sutter family, shows Laura she is more than just a weapon and gives her the power to escape the demon's influence, saving both herself and Julian.
- Issue #9 of Superior Spider-Man features a showdown between Otto Octavius and Peter Parker, who, after his death in Ock's body in ASM #700, exists as a 'ghost' in his own body via all his memories given consciousness. Otto begins to purge Peter's memories through one of his devices in order to get rid of him, but Peter fights back, forcing Otto to go in and eliminate Peter himself. In the Mindscape, Peter summons the memories of his friends and family to subdue Otto. But, Octavius, having looked back at Peter's memories for months, summons the memories of all his enemies, who "kill" Pete's friends, which erases his memories of them. Peter is horrified by his loss, but regains confidence and turns in the Amazing Spider-Man, and Otto follows by turning into the Superior Spider-Man. Both fight and look at the reasons why the other one fails at being Spider-Man; Peter discusses Otto's brutality, and Otto discusses Peter's Thou Shalt Not Kill rule and the indirect problems it caused. Otto wins by pointing out Peter's Moment of Weakness - risking the life of a girl while Otto was performing brain surgery on her, so that Otto wouldn't get the tech to find Peter in Otto's brain. Peter is defeated and ashamed of himself. Otto declares that he is superior to Spidey and manages to successfully erase Peter from his brain.
- Multiple battles occur in the Death Note fanfic "Zenith, Darkness, Reverie," as the protagonist and Kira attempt to determine which personality should be granted control of the body, the Death Note, and, by extension, the world.
- Kind of happens in A Spark of Genius. Boston Brand finds Xander meditating at Rama Kushna's temple and has no idea who he is. Instead of appearing before him and, you know, asking, he decides the only way he could figure out who he is is by going into his mind and reading his memories. Boston promptly gets sucked into Xander's mind, wherein his many personalities take turns kicking his ass. The goddess herself has to intervene and take away Boston's memories of Xander, or else Xander would have actually killed him.
- An interesting version occurs in You Obey, where it is the protagonist who initiates the battle.
- A big part of the fight with Future Cell in Honor Trip. Cell tries everything in his power, including Talking the Monster to Death, and harassing his captor by beat-boxing a taunt.
- In the Doctor Who fanfiction "Who's Afraid of the Big Bad Wolf," Rose is kidnapped and Mind Raped by aliens who want to use the remnant of the Time Vortex in her mind. To prevent them from finding the information they need, she rips apart her mind from the inside out. The aliens, instead of giving up, sort through the rubble (described as a beach, each grain of sand being a memory) for months. Too bad they forgot to figure out how to control the time energy once they released it.
- Gekizetsu's series The Month of Open Doors begins with Supernatural's Dean Winchester locked in a room in his own mind by something. A rather strange battle in the centre of the mind plays out over the first arc, As Fools Shine On.
- The Homestuck fanfic Darkness climaxes in John, who has gone utterly insane, fighting an Evil Twin. On the outside, of course, he's gone into a coma.
- Because Mind Rape was a staple of Galaxy Rangers, the Fanfic tends to break out this one quite often. Red Witch's Down the Dark Path plays it straight after Shane was tortured with the Mindnet. "Isn't Life Strange" and "Chrysalis" use it as well. Subverted in those fics as the Rangers affected lose - badly. It's played straight in both later, though.
- Used in the DC Nation universe after Raven's attempt to restore some of Troia's lost memories end up getting Raven, Troia, Nightwing, Flash, and Arsenal in a brawl with Dark Angel. Leads to one of Arsenal's best lines:
Arsenal: "All you're telling me is that I've pissed in your Cheerios more than once, and I did it beside Donna. Lemme tell you, those are two things that make me a very happy little camper...And hey, extra bonus for me at the end of it? I pissed you off when I didn't even mean to! Little ol' me. A guy. A dude. A very attractive but semi-normal human fleshbag. Man, I'm good."
- In the Daria/Legion of Super Heroes Fan Fic crossover Legion of Lawndale Heroes, psi-active cadets at the Military School known as the United States Academy of Extranormal Studies, or 'USAES' , can receive certification in the Astral Special Tactical Response Operations (ASTRO) course for out-of-body and psionic combat. As part of their training, cadets learn how to create a specific 'mental persona' (much like a 'Patronus') to do mental combat in and manifest their powers during that combat.
- Taker Foxx's Imperfect Metamorphosis has so far in the story four characters sharing a same body because the jelly monster can absorb other characters. It doesn't help that one of them came with a Super-Powered Evil Side. There is a Battle in the Center of the Mind between the host and the villain when the villain is discovered.
- Implied in this fanvid for TRON: Legacy (spoilers out the kazoo).
- The dwarven noble protagonist of Dragon Age: The Crown of Thorns had more than one of these, twice against actual psychic attacks by the Archdemon. The latest one had rather severe consequences for both the prince and the whole world because the Old God actually evolved because of contact with the exile's Magnificent Bastard-level intelligence.
- Kallian Tabris also goes through something like this at one point, only it's a projection of her soul, taking Faren's form (the dwarven commoner, her love interest), that does the actual fighting.
- My Little Pony: Friendship Is Magic fanwork The Party Never (or Hasn't) Ended features Twilight Sparkle having to help Pinkie Pie in one of these against Nightmare. Then Pinkie Pie helping Rainbow Dash. Then Pinkie Pie by herself. And it is awesome.
- Queen of All Oni: Throughout the story, we get glimpses inside of Jade's mind, where we watch as Hero (the Aspect representing Jade's heroic nature) gather together as many uncorrupted Aspects as he can into a La Résistance aimed at regaining control of Jade's mind from The Queen. They eventually launch an attack on the ship representing Jade's consciousness, but before Hero and The Queen can fight each other, the trope ends up being subverted — in the real world, Jade is captured by the Evil Sorcerer Lung, whose attempts to break Jade to his will end up driving her insane, which cause the mindscape to literally fall apart, forcing the Aspects to focus on their own survival. When Jade's mind is restored, The Queen captures Hero, ensuring her continued dominance of Jade's mind.
- Happens a couple of times in the Pony POV Series:
- First, during Pinkie Pie's reharmonizing chapter, Angry Pie (a Split Personality representing all of Pinkie's anger) attempts to pull a Split Personality Takeover by absorbing all the other pieces of Pinkie's mind. Pinkie is only able to defeat Angry by performing a Split-Personality Merge with her Pinkamina personality and then forcing the merge on Angry as well.
- This is also the conclusion of the Trixie storyline: Twilight enters Trixie's mind to free her of her discording, and is confronted by Trixie's Enemy Within, Loneliness, who fights her at every turn. Eventually, Twilight gets through to Trixie, who accepts her help, and together they destroy Loneliness.
- This also pops up at the end of Bright Eyes' entry of the 7 Dreams/Nightmares collection: she's dragged into her Mental World by an entity claiming to be her Enemy Within Cruel Eyes, but is actually the Shadow of Discord's eldest brother D___t, who's trying to absorb her soul and potential concept in order to reconstitute himself. With the love of her friends and family, Bright Eyes is able to defeat D___t, being sure to destroy his Shadow even after mortally wounding him in order to make sure he stays gone.
- Happens at the climax of Getting Back on Your Hooves: After Checker Monarch's Engineered Public Confession, she snaps and casts a mind spell to trap Trixie and her friends in their worst nightmares in order to break them. Thanks to a Lucid Dreaming trick Trixie taught them earlier, the girls are all able to see the flaws in the dreams and take control of them, before forcing the pieces of Checker's consciousness attacking them out. Said pieces fuse together and try to destroy them, but they easily defeat it. They then travel to Trixie's dream, where she's being attacked by the main part of Checker's mind, and give her the strength and encouragement she needs to fight back and finally defeat Checker.
- A Growing Affection has a battle between Naruto and the Kyubi while Naruto is sedated by the Akatsuki and they are unraveling the seals on the demon. The weakening of the seals allow the Fox to create a clone/fragment that can slip through the cage and fight Naruto.
- Variant Strain has Peter doing this against Hank.
- The World of the Creatures takes place in the mind of the author/protagonist. It acts as the setting for a Massive Multi Player Crossover Fic where various characters from different franchises face off against an idea-eating monster.
- In Yugioh The Thousand Year Door, Diana has a small battle in the center of her soul to free herself from the Shadow Queen's Mind control.
- While journeying into Socrates' mind to repair a faulty transmitter chip in Calvin and Hobbes: The Series, the protagonists find it along with his dark side, who then fights Hobbes. It's a somewhat downplayed example, as the emphasis isn't on the battle but rather Calvin and Andy trying to repair the chip.
- In The Swarm of War, the Overmind has one against Ahzek Ahriman. Turns out, even one of the most powerful psychics in the galaxy cannot match a world spanning Hive Mind.
- In The Mind of the Doctor the Doctors battle against the Dark Side of them who has been freed by the War-Feeder.
- Happens to Han Solo in the Star Wars fic My All. In the fic it's a sequel to, Han was brutally tortured and raped. Somehow, his attacker seems to have transferred her essence into Han's body when Leia killed her. Han ends up having to battle it out inside his mind to not only get rid of her, but put his own struggle to rest. Luke uses a risky force technique to enter Han's mind, though Han kicks him out the first time. Luke is able to watch what is happening, but the fight is all up to Han.
- Happens (twice technically) in the Naruto fanfiction Catch Your Breath:
Kei—the Dreamer—says, “Running interference. The compulsion affects the dominant personality—the kunoichi you both know. She is stalling. As for the Tailed Beast, the Three-Tails activates hindbrain impulses toward destruction and rage in order to weaken the seal, personified and confronted by Id. I am neither, and have been forced to act in their stead until the situation can be resolved.
- When the Three Tails was sealed into her, one of Kei's split personalities was fighting him (to stop him from escaping), Kei herself was fighting the Mind Control seal Madara put inside her, while the second split personality was controlling the body and fighting external threats.
- In Thousand Shinji:
- Shinji and Asuka fought Leliel together in the psychic plane.
- Asuka's battle against Arael consisted in Asuka putting up her psychic shields and barriers up while Arael blew them apart, and trying to endure the mental onslaught until she was capable to blow the monster up in the physical plane.
- The Final Battle in Children of an Elder God happened simultaneously in the mental and physical planes against the dead Outer Gods.
- Last Child of Krypton: Shinji fought Leliel in an illusory dreamscape to save Asuka’s mind.
Films — Live-Action
- In the film Dreamcatcher, based on the Stephen King novel, one of the characters is possessed by an alien being. In his mind, he locks himself in a warehouse of his memories and tries to bar the alien presence from getting inside.
- Harry Potter and the Order of the Phoenix makes good use of this in sequences throughout, especially at the end when Voldemort attempts to possess Harry. Voldemort imprints Harry with the memories of all the loved ones he has seen die by that point at Voldemort's hands, before Harry turns it back on him by noting that he truly pities him for his inability to feel love or the joy of friendship.
- In the psychedelic western Renegade (aka Blueberry) based on the graphic novel, the hero takes peyote and gets into a spirit battle with the villain. The forces of good are golden reptiles, while the evil side are black bugs. After defeating the villain, the hero watches a recreation of a forgotten tragedy and comes to terms with it.
- In the Chinese film Hero Magistrate Nameless makes a show of attempting to arrest Long Sky at a Chess Court in his prefecture. They pause mid-fight, Nameless paying the resident (blind) GuQin master to continue playing. This he does, as they fight out the remainder of the battle in their minds. When he breaks his instrument with the sheer intensity of his playing, the fight plays out for real and Nameless defeats Sky in a matter of seconds.
- Inception takes this trope and turns it Up to Eleven. Virtually the entire plot takes place inside a dream, battling defensive figments called 'projections' while trying to plant the Idea in the subject's mind. To make things worse, the specter of the protagonist's dead wife haunts his steps.
- Sherlock Holmes: A Game of Shadows features an example similar to Hero: When Holmes and Moriarty have completed a game of chess and Holmes reveals the full extent of the damage he's done to Moriarty's ambitions, Moriarty walks up to him in full Tranquil Fury, pausing to give Holmes a last light on his pipe. As this happens, Holmes begins a Sherlock Scan to analyze the fight that's going to start in a moment and make his plan of attack, only for Moriarty to smile at him and continue the analysis; both play out the complete battle in their heads, and both foresee an inevitable No-Holds-Barred Beatdown that results in Moriarty beating Holmes to death and throwing him off the balcony. With no situation in which he can defeat Moriarty and both of them well aware of it, Holmes goes for the one thing Moriarty didn't predict in their mental battle; a Taking You with Me attack.
- In the Guy Ritchie film Revolver, the protagonist Jake Green, who is claustrophobic, battles his ego when he gets trapped in an elevator. What follows is a scene that looks straight out of the last episode of Neon Genesis Evangelion.
- Avengers: Age of Ultron:
- A cyberspace variant occurs shortly after Ultron wakes up and he and J.A.R.V.I.S. have a software war, complete with dueling code.
- A rematch of sorts happens when Vision first clashes with Ultron and Vision cuts off Ultron's access to the Internet, trapping him in his physical form.
- In The Last Witch Hunter, Chloe invades Ellic's mind to cut off the spell he's chanting and they have a literal knife fight in the middle of his memories. Justified by Your Mind Makes It Real.
- In an Australian student film, a supervillain has killed the Captain Space, Defender of Earth! then challenges his Defiant to the End sidekick to this trope; "you versus the overwhelming force of my ego!" as the villain puts it. Their conflict is shown as them playing hero and villain in a series of movie clips — a Dastardly Whiplash tying the hero to the railroad tracks in a silent film, a Swashbuckler Sword Fight, a World War II movie, and a switchblade fight in a 70's 'blackboard jungle' film.
- The stand off with the Volturi in Breaking Dawn can be interpreted as this, as Bella used her vampiric ability to block out powers to protect Cullen allies from Jane's ability to telepathically cause pain to others.
- In Terry Pratchett's Thud!!, when Commander Vimes is chosen as the Summoning Dark's champion, its attempts to take him over are represented as it entering a city (Vimes's mind) and being thrown out by a Watchman, representing the bit of Vimes that watches himself: the Guarding Dark.
- This also shows up in A Hat Full of Sky, where the Nac Mac Feegle help Tiffany confront the hiver that's taken over her body by luring it into the part of her mindscape where she's most powerful, a mental representation of her home country.
- Granny Weatherwax has a moment like this in Carpe Jugulum. (Vimes and Granny have a lot in common...)
- Rincewind has a Hissy Fit In The Center Of The Mind in The Light Fantastic, when he berates the Great Spells of the Octavo for ruining his life, and he later subdues the Eighth Spell by figuratively hauling it out of hiding within his psyche.
- In the final book of Grey Knights trilogy, Alaric fights a battle for his soul with a daemon while trapped in his mind, which the daemon has already taken over. He ends it by Taking You With Me, but survives.
- In The Elric Saga story The Blood Red Game, humans and their allies escape an imploding universe and want to settle in another. When they do, they encounter aliens. Said aliens would issue a Curb-Stomp Battle in a physical fight, but they agree to play their "Blood Red Game" to allow humans to settle. Said game is a Battle in the Center of the Mind. Losers become catatonic or insane.
- Magician. Tomas, one of the main characters, finds a suit of cursed armor that fuses him with a godlike being, who wants to repulse the invaders (Tsuranii). Said godlike being was one of a race that created the bloody elves as their personal slaves, to the point that an elf can't disobey any word said in their language, and who are fiercely protective of their world. Now, if Tomas standing in the middle of a storm of pure mental fury from a dragonlord whilst quietly saying, "I am Tomas" isn't an incredibly badass version of this, nothing is.
- That "godlike being" is actually a Dragon Lord, or Valheru as the elves call them. They weren't really godlike, as they all got slaughtered except onenote when they challenged the Lesser Gods of Midkemianote during the Chaos Wars, but they're still far more powerful than any human or elf except the highest levels of magician.
- The ally-assisted version was used in the book Prince of the Sidhe, when King Aedh of Eiru (Ireland) gets drugged by the book's villain. We see Aedh's mindscape (which is just as confused as he is), and get things from his point of view when the titular character comes to Aedh's assistance in his own unique fashion.
- in the sixth Young Wizards book, the autistic wizard-to-be Darryl is subjected to this constantly - his "Ordeal" (a battle with the Lone Power to prove fitness as a wizard) has gone on for three months. The reason for this is that he's an abdal, a physical embodiment of God's power, and the Lone Power (Satan) fears the amount of power he'd have if he did make it as a wizard. Eventually Nita and Kit get into the kid's head to help him break the cycle.
- George R.R. Martin's "The Glass Flower" has pretty much turned this whole concept into a story. He calls it 'the game of mind'.
- In the Warhammer 40,000 Imperial Guard novel Cadian Blood, Seth in a Last Stand against a daemon. When the daemon kills him, he dies laughing and saying the look at the daemon's face made the fight worth it.
- Lasciel was doing a pretty good job of screwing with Harry Dresden until he realized that even a fallen angel is at his mercy when it's in his head. Pwnage ensued.
- Also Harry vs. Leonid Kravos, slugging it out in Harry's dreamscape at the end of Grave Peril.
- Molly fights an epic one against the Corpsetaker in Ghost Story. Apparently, the center of Molly's mind looks like the bridge of the 1960s Enterprise, complete with a crew of Mollies wearing miniskirt uniforms and mimicking the behavior of the original characters and an epic fighting music soundtrack.
- Not to mention the miles of incomprehensibly intricate battlefield outside of the bridge. The fact that Corpsetaker gave up attempting outmaneuvers and just started smashing everything until she overpowered Molly says a lot about how good Molly is at this illusion stuff.
- In Cold Days, we see Harry get into several of these, including one with Mab's boss which, if he lost, would mean his execution. And another when he battles against Sharkface, an Outsider.
- Julia spends most of The Ragwitch trying to find a way to make some headway Fighting from the Inside the titular monster. Towards the end, this culminates in a real battle when she, Lyssa, and the personalities of the king and the original witch who was subsumed into the Ragwitch fight for continued existence after the Ragwitch finally realizes that Julia hasn't been as helpless as she thought. A dragon and hordes of mooks are involved.
- Dandra and Tetkashtai get one during the climactic battle of the second book in The Dragon Below trilogy. Though it is less of an invader vs. invaded than two splinters of one personality duking it out to see which will be dominant.
- The Star Wars Expanded Universe Darth Bane novels use one of these to settle the legacy of the Sith. The inevitable battle between Bane and Zannah takes place when he tries to take over her mind. while Bane was better with the saber than Zannah was, she proved a superior sorceress. There is still a small trace of him left in her, though.
- Chronologically much later, in the New Jedi Order novel Reunion, Jedi Knight Tahiri gets sucked into one of these by her Enemy Within, an artificially implanted Yuuzhan Vong personality who is trying to pull a Split Personality Takeover on her. It turns out that neither of them can win, since they've become so tightly linked that destroying one would destroy the other; to save their sanity, they end up doing a Split-Personality Merge instead. The whole thing is represented as a sort of really trippy lightsaber duel with injuries carrying over to both combatants.
- In Tim Powers' On Stranger Tides, the confrontation between sorcerers Leo Friend and Benjamin Hurwood concludes when the former attempts to re-write his own memories to bolster his own self-confidence, and therefore his power. The latter undermines his enemy's attempt to rewrite history in his own mind, crushing his opponent's psyche by exaggerating his recollection of a traumatic humiliating event.
- The ending of Robert Sheckley's The Status Civilization is this. The Earth civilization brainwashes children to make them responsible members of society - and this brainwashing includes strong urge to report on oneself in case of committing a crime (or even being in a situation where you can be a suspect) and to commit suicide in case these lessons are ever remembered consciously. Barrent was sent to Omega because he confessed in a crime he never committed, returned to the Earth and had to fight these old urges that took form of the worst memories he got from Omega.
- In the Star Trek: The Next Generation Mirror Universe novel Dark Mirror by Diane Duane, Deanna's mental defences are represented by children's building blocks (when she was being taught to use her powers she heard the term "mental block" and misunderstood). Evil!Deanna batters ineffectively against these blocks, while our Deanna calmly walks into her opponent's mind as though it was her own, because unlike her counterpart, she can admit that, in a way, it is.
- The Doctor Who New Adventures novel Timewyrm: Revelation by Paul Cornell is largely set inside the Doctor's mind, which is under attack from the Timewyrm. Different parts of the Doctor's mind are looked after by five of the six past Doctors (Sixth isn't there for reasons we learn later), and there's an area where the six "embryonic" personalities of Doctors-to-come wait to be born.
- In Sergei Lukyanenko's Night Watch series, the battle for dominance between Vampires apparently works like this. To an outsider, however, it looks like a glorified staring contest.
- In Very Bad Deaths, an oversensitive telepath is forced to confront a serial killer. Despite only one of them having psychic powers, this is a genuine battle, as Alan's thoughts are so vile as to be weaponized.
- The Novel Guild Wars: Edge of Destiny has an interesting Example. After being engaged in a fight with the Eldritch Abomination Kralkatorrik, Snaff enters the [[spoiler:dragon's mind to prepare it for the Finishing Move and finds himself in a raging storm (a metaphor for Kralkatorrik's anger). He eventually manages to calm the beast and leave it behind in a catatonic state making it vulnerable to an attack. However, they failed anyway.
- In Up Jim River from the Spiral Arm series, the scarred man suffers a mental breakdown caused by conflict between his ten split personalities and ends up fighting a battle in his mind. Nine of his personalities team up to destroy the tenth, which was suicidal and trying to cause the scarred man to die.
- Something like this is a major form of combat in the Inheritance cycle. Wizards/witches/sorcerers/magicians/Riders battle each other by attempting to break into each other's minds, then using this to predict what the opponent will do and countering it.
- Farscape made this into an art form with John's confrontations with Harvey-Scorpius. This resulted in one of the best episodes anywhere ever: a Looney Tunes style cartoon showdown, including all the old favorites (painting a wormhole on a wall only for someone to drive through it...).
- In the Doctor Who serial The Deadly Assassin, the Doctor and the Master tap into The Matrix (a psychic computation matrix) and have a battle of the wills—the landscape in the Matrix is created by their brainwaves, so the Master can basically create an entire world through his will and makes the Doctor suffer various tortures in it, nearly killing him.
- In The Three Doctors, the Third Doctor and Omega have a mental battle in which Omega is represented by a goblin-like creature.
- Recently one in Nightmare In Silver where the Doctor and Mr. Clever battle for full control of the mind, although they use a physical game of chess in place of a psychic battle.
- Highlander: The Series' Duncan MacLeod has two of these:
- The first one while under the effects of a "Dark Quickening", between his noble self and the evil he has absorbed through centuries of beheading evil immortals.
- The second one against the demon Ahriman.
- The Red Dwarf episode "Gunmen of the Apocalypse" has the main characters enter Kryten's subconscious to help him fight off a computer virus.
- Also in "Terrorform" when the crew face off with Rimmer's Self Loathing monster and later when Rimmer's ressurected self-confidence defeats his inner demons, saving the crew.
- Angel vs Angelus, with Faith present as well.
- During Power Rangers Dino Thunder, Tommy spent several episodes stuck his Ranger suit, then unable to turn his invisibility power off so that his actor could visit his family. His first episode back involved him becoming visible again, but putting himself into a coma in the process. He then had to fight his previous Ranger identities. After barely getting past Zeo Ranger 5 and the White Ranger, he had his ass thoroughly kicked by the Green Ranger, but still refused to quit - at which point they allowed him to wake up and restored his Dino Gem into the bargain.
- Happened a couple of times in Stargate Atlantis, memorable examples being Dr. Weir facing off with Oberon in her mind to allow her teammates to escape the other Replicators, Teyla fighting off the Wraith queen's attempts to probe her mind, and Sheppard fighting himself (sort of) in his own mind.
- During the Supernatural season six finale, the wall around Sam's memories of being in Lucifer's cage is destroyed, shattering his psyche into pieces - "normal Sam", the Sam who spent a year without a soul, and the Sam who remembers Hell. Normal Sam kills and absorbs soulless Sam, but the third Sam has no interest in fighting and begs Sam to stay in the dreamscape and spare himself the memories of what happened. When that fails, he allows Sam to absorb him.
- In The United States Of Tara, Tara held a conference in her head with her various alters in order to draw up a contract between her and them.
- In the Star Trek: Voyager episode "Warlord", the mind of a ruthless dictator forces itself into Kes, but she manages to fight him off mentally.
- Red vs. Blue (more specifically, Church and Tex) took a trip into Caboose's mind while he was semi-possessed. Interestingly, the actual fight against the evil force is done against a backdrop of the actual Red Vs Blue war ... with a few unique ideas of who's involved.
- "The Trial", the climax of Pink Floyd's 1979 Rock Opera The Wall, features the main character put on trial in his own mind and convicted by a monstrous imaginary judge.
- Kitananx made a song CALLED Battle In The Center Of The Mind.
- "Heaven Tells No Lies" by Helloween invokes this in the chorus:
I'd need a shotgun in my dreams tonight
To terminate my rotten side.
- In Yu-Gi-Oh! East Academy Sigmund has one against his partner spirit Freed. However, it's inside Freed's mind rather than his own.
- Dungeons & Dragons
- Illusion spells 'Phantasmal Killer' and 'Weird' work a lot like this trope, in that they create a personalized Imaginary Enemy that get killed the targets who fail to resist their terrors.
- In Ravenloft, recurring nightmares occasionally attract the attentions of a group of darklords called the Nightmare Court, who, as their name suggests, try to play it up until they reduce the ailing victim into a comatose wreck. Needless to say, any adventure involving them is about kicking their ennui out of the head of the dreamer while sorting out his issues.
- The Dark Sun sourcebook The Will and The Way introduced "harbingers" and "constructs" — mental forms that tweak and help to focus telepathic combat powers (the question whether both sides see the same is avoided, since on Athas psionics is well-codified). So you end up with mental attacks and defences put into images such as a giant scorpion trying to undermine a wall or flames trying to burn through a beetle's carapace.
- A possible occurrence in the "Zorandar" setting from Hero Games' "Lands of Mystery". If you get captured by one set of enemies, they'll try questioning you telepathically. Resist, and the telepathic struggle is gamed out as a one-on-one fight between your interrogator and you. If you lose the fight, the interrogator gets the answer to whatever question set this in motion. If you win, you wake out of the mind trance to find your interrogator has just suffered a brainfry (and if you can't figure out that this is the perfect time to escape ....)
- The Sidereal charm Meditative Battlefield Escalation in Exalted works this trope somewhat in reverse. Instead of an invading force attacking a defender's psyche, the Sidereal creates an entire battlefield in their own mind and draws their enemies into that. Then they have supernatural Fist-fights in the center of their own mind.
- Deadlands sees one of these happen if someone becomes Harrowed. Their soul wages war against the manitou in their body, in a setting based on the character's worst nightmare. The winner gets to control the body.
- In Dungeons & Dragons Online, the quest 'Finding the Path' involves protecting your mind (embodied in a glowing orb) against the assault of Dreaming Dark creatures, before confronting the cultists in real life.
- Raz in Psychonauts fights (and helps defeat) the Freudian Excuses lurking in people's brains — such as a painter's anger (which manifests as a bull), a former insane asylum warden's split personality (which looks like Napoleon and against whom he is constantly trapped in a war game), and even the Big Bad's and his own father issues, which manifest as an enormous butcher and a taunting zombie ragdoll, respectively.
- In Drakengard 2, Nowe fights one of the boss battles in Manah's mind after she has her
HeroicVillain Protagonist BSOD.
- If you decide to attack the Mindflayer Elder Brain in Neverwinter Nights: Hordes of the Underdark, it will suddenly trap you inside an illusion where you are waking up from a dream. If you accept it, you get a non-standard game over. If you reject it, you will be attacked by monsters within the dream and upon defeating them you will return to reality and the Elder Brain will beg for mercy, allowing you to make a deal with it or deal the killing blow.
- In Splatterhouse 3, Rick fights the final boss, the Terror Mask, in an Amazing Technicolor Battlefield that represents his psyche.
- Kingdom Hearts:
- In Kingdom Hearts: Chain of Memories, when Riku fights off Ansem.
- And there's another one in Kingdom Hearts II, Sora vs. Roxas.
- Special mention too that the Awakening seems like a semi-physical place, since Donald and Goofy mention Sora disappearing from the scene.
- Happens yet again in Kingdom Hearts: Birth by Sleep with Ven vs. Vanitas and Terra vs. Master Xehanort, with Aqua pitching in during the True Final Boss fight. The secret ending suggests that Terra and MX spent years vying for control of the new Xehanort's heart.
- Unfortunately, the next game in the series, Kingdom Hearts 3D: Dream Drop Distance strongly implies that that last battle in the center of the mind from Birth by Sleep only lasted for a year rather than the several years we were led to believe, and we have yet to learn what happened to the loser.
- Cranked Up to Eleven in the same game, where it turns out Riku had been fighting off the Nightmares within Sora's dream imaginings of the Sleeping Worlds. His boss fight with Ansem also takes place in the "Darkness within Darkness" of Sora's dream. Then, in the True Final Boss fight, Riku fights off the Armored Ventus Nightmare within Sora's Heart.
- In American McGee's Alice, the purpose of Alice's nightmarish return trip through Wonderland is this.
- The Incredible Hulk: Ultimate Destruction has a boss battle in Bruce Banner's subconscious, where the Hulk takes on Banner's underlying hostility and malevolence, officially dubbed "Devil Hulk".
- Sort of happens in Earthbound, as Ness has to fight his own Nightmare at the end of his dream world known as Magicant. (Averted in Mother as that Magicant is Maria's dream instead of Ninten's. A fight with Lucas' Nightmare was removed from Mother 3, which has no Magicant.)
- Happens near the end of Planescape: Torment when you have to enter a mindtrap and meet three of your most important previous "incarnations" inside. If you manage to take them over or merge with them, you gain their memories and a lot of XP. If you fail the merger you have to destroy them, which gets you no memories or XP. The success of the merger is determined by stats and conversation options, one can only be taken over if your willpower is above a certain level, while another is much easier to convince to merge if you can gain his trust by convincing him that you and him are the same person.
- Late in Jeanne d'Arc, Jeanne, Gilles, and Richard are whisked into an abstract representation of Roger's heart, bound by chains by the Reaper Ira. The three of them must battle Ira's cronies to destroy his power over Roger; eventually, a manifestation of Liane's spirit joins the three heroes to assist them, particularly because her death is what caused Roger to submit to the Reaper.
- In Final Fantasy VI, sleeping at Doma Castle with Cyan in the party will cause the party to be taken into Cyan's mind, where they can battle a demon called Wrexsoul that is feeding off his survivor's guilt.
- Also, the final battle of Final Fantasy VII happens inside Cloud's mind. He destroys Sephiroth in one strike.
- In Shin Megami Tensei I, you find a young girl (actually the reincarnation of the Heroine) whose mind has been infested by a demon that is devouring her from the inside-out. You have to dive into her mind in order to kill the demon and save her.
- Tales of Symphonia: Dawn of the New World: If you go for the good ending, this is the final battle. Given how different Emil's and Ratatosk's personalities were, though, the player was probably expecting something like this to happen (although it's a lot less confrontational than you might expect — whichever way the fight turns out, the two accept each other).
- The battle against The Dark Prince in Prince of Persia: The Two Thrones turns out this way. After some platforming, you end up with him and you, the solution being to stop attacking and walk away.
- Although annoyingly, even if you attack he can't kill you. All that happens it that you need to walk through an army of Dark Prince clones.
- Happens no less than three times in Jade Empire:
- Two demons vie for control of a little girl's body. You have to pick which one you'll support, and then it's a kung fu battle inside her mind.
- Near the end of the game, you can attempt to wrest control of The Dragon away from the Big Bad. You control the ghost of the Dragon's past self and fight its current incarnation.
- When you confront the Big Bad himself, he attempts to overwhelm you with despair. Naturally, this means you have to fight some freaky glowing swordsmen named "Despair" in an Amazing Technicolor Battlefield. You also get to rely on the Power of Friendship for encouragement, which takes the form of your allies running up to the "Despairs" and, um, exploding.
- The Kalecgos encounter in World of Warcraft: Burning Crusade. The players are supposed to free the good dragon from a dreadlord that is mind controlling him.
- An odd example where you're the invader is in the fight with the monster of dubious quality, Yogg-Saron. During the fight with him, portals into his mind open up, where you to disperse projections visions of an important event in Warcraft lore so that you can access his brain. Of course, he knows you're in there, and he will attempt to whittle down your sanity and put you under permanent Mind Control, so you have to inflict damage on Yogg-Saron's brain as soon as possible and leave quickly.
- In Arthas: Rise of the Lich King, Arthas winds up in a rather one-sided battle when he dons the helm of domination; he's in a room in his mind with Ner'Zhul, the orc Shaman that became the Lich King, and a cowering child that represents the last of Arthas' humanity. After all is explained, Arthas runs his humanity through without hesitation... and then does the same to Ner'Zhul when he approaches to congratulate him. It doesn't end here though, as it's revealed in the game proper that the fragment of Arthas' humanity survived as Matthias Lehner, who kept Arthas just human enough in the depths of his heart that he held the Villain Ball instead of annihilating all life on Azeroth as easily as he should have been able to.
- Every boss fight in Persona 4 is this until close to the end of the game. Although it's more like "Battle In The Center Of The Collective Unconscious".
- Not quite the same, but not quite anything else either: In Maken X, Kei's consciousness (using Kei's form) spends most of the game standing on a glassy-looking disc in her brain yelling/screeching at her body, now possessed by the Maken.
- Near the end of Sam & Max: Freelance Police "Culture Shock", Sam falls under the hypnotic sway of disgruntled former child star Brady Culture. After snapping himself out of it by a blow to the head from the security system at Bosco's Inconvenience Store, Sam finds himself in his own mind. There, he has to dispose of a host of Brady Culture clones that represent Culture's hypnotic influence.
- The finale of Arcueid's and Archtype Earth's plots in the "Current Code" version of Melty Blood is this between them.
- Battle Moon Wars has this in Tohno Shiki's mind while he lies unconscious, fighting internally against Nanaya Shiki. Unfortunately for him, he also visualizes Akiha and Satsuki in this mindscape and thus is unwilling to fight at first. Insert friendly telepath encouragement as Sion uses Etherlite to join in and help him out.
- Psychic Force 2: the final battle in Emilio's story mode sees him fighting his dark side in his mind. He loses.
- The final battle in Dead Space 2, where Isaac fights Nicole and the Marker
- A rather weird one in No More Heroes 2: Desperate Struggle where Henry, while unconscious, fights against Mimmy, a manifestation of Travis' various fetishes (being a Moe Robot Girl), which is apparently brought on by Travis "watching" anime in the other room.
- Anyone in the Penumbra series who gets infected by the Tuurngait gets one of these, although you only play through Philip's. He and Red both win their battles, retaining a measure of self-control (and, in Philip's case, splitting off his own infestation from the Hive Mind to make it an easier-to-manage Enemy Within.) Everyone else who appears in the series lost and got assimilated.
- Happens twice Batman: Arkham Asylum when Batman gets drugged by The Scarecrow, resulting in massive Interface Screw and a Fission Mailed before entering a twisted world based on his psyche. However Batman fights it off due to Heroic Willpower, to the horror of Scarecrow. It also happens in the sequel with the Mad Hatter and one last time in Arkham Knight which involves Batman fighting off the last memories of the Joker and sealing them away.
- In The Elder Scrolls V: Skyrim, Sheogorath takes you to his personal vacation spot: the mind of Pelagius the Mad and will only agree to leave if you humor him and combat Pelagius' various psychoses with the help of his artifact, the Wabbajack.
- The climax of Metro 2033 The protagonist is mentally fighting the Dark Ones, who are trying to stop him from annihilating their home - all while the protagonist is on the highest point of Moscow's Ostankino tower as it's crumbling. Failing the fight results in the protagonist falling to his doom from the mental blow.
- The Very Definitely Final Dungeon of Neverwinter Nights 2: Mask of the Betrayer has you and possibly a companion battling the Spirit-Eater itself for control of your soul.
- Pokémon Mystery Dungeon 2: Marill's brother, Azurill, is locked in a nightmare and unable to wake up due to a legendary Pokemon that can infiltrate and attack other beings in their dreams: Darkrai. With the help of an ex-con Drowzee, the hero and his partner are transferred into Azurill's mind to figure out the cause of the problem.
- In Kingdom of Loathing, one of the annual Mr. Store familiars for 2013, the Angry Jung Man, drops psychoanalytical jars that let you copy and explore the psychoses of various non-player characters, such as the Crackpot Mystic, the Pretentious Artist, and the Suspicious-Looking Guy.
- In Blades Of Othersides, Kona is constantly fighting one with his Super-Powered Evil Side. Which side is presently winning affects which form he's in in the physical world.
- If the player presses the B Button during a certain important event in The Halloween Hack, Varik enters Dr. Andonuts's mind and discovers the reasoning behind his insanity... And then he winds up fighting Dr. Andonuts' personal demons as well as the doctor himself.
- Twisted Metal Black takes place entirely in Needles Kane's head, handily handwaving the more extreme-concept characters like Dollface or Charlie Kane.
- When Painwheel attempts to reject Brain Drain's mind control in her story mode, the battle is visualised as a Mirror Match against a Painwheel-bot coloured to resemble Brain Drain. This battle also transports the scene from Maplecrest to Nightmare Crest - a twisted version of the Maplecrest stage where the surroundings are black and muted, the leaves are frozen in mid-fall but the sky is red with rapidly-swirling purple clouds.
- Fukua is (in-universe) a clone of the protagonist Filia, and whose story mode consists of her battling all the other characters in Filia's dreams as she sleeps. Fukua's final opponent is Filia herself inside Filia's mind, and the fact that the fight also takes place on Nightmare Crest suggests that the dream has just become a little too real.
- The sixth arc of Umineko: When They Cry involves a duel between Shannon and Kanon that is a thinly-veiled version of this, with Beatrice sitting on the sidelines. The seventh arc reveals that this has been the state of affairs within Sayo Yasuda's head for a good year or two prior to 1986. Once Beatrice is forced off the sidelines by Battler's return, the entire duel is scuttled, however.
- Liquid's battle against the Ghost of Big Boss for control of his body, in The Last Days Of FOXHOUND.
- Dominic Deegan, several times. The titular character's main strength is his mental abilities. And it's established that on the psycho planes, a being's physical size is directly proportion to how powerful their minds are.
- Shows up in Schlock Mercenary when the titular carbosilicate amorph is infected with nanites that hack into his brain. When Schlock pulls out his plasma cannon, the nanites are initially unimpressed:
Nanite: Look, we told you already... that thing won't work in here. It's just a metaphor."Schlock: But a meta for what? I have a pretty good immune system...
- A variation occurs in Charby the Vampirate when Tony has to use his Alp powers to enter Zeno's mind and help him fight the spirit possessing him. Turns out that Zeno has pretty much given up the fight already and is of no help, so Tony changes tactics and get the spirit to not only force him out but to enter his mind instead. A big mistake, as it gave Tony a massive homefield advantage.
- Torg from Sluggy Freelance faces one of these during the "Wayang Kulit" Story Arc. In this case he's fighting all of his major past and current Love Interests. Bit of a subversion, in that killing them only makes things go worse for him.
- K in Blip, when she was in rage. First she kicked out her friends, then for lack of semi-real targets imagined and destroyed a Pirate Transvestite Robot.
- The Order of the Stick: Haley’s “mental constructs” have a habit of bickering amongst themselves, at least until she makes them all sit down and shut up.
- Happens between Artie and Joel in Concession, but ultimately spills over into the real world. Doubles as a subverted "I Know You're in There Somewhere" Fight as unfortunately, that part only works for a little bit.
- Monique from Sinfest once tried to defeat a rhinovirus with(in) her mind.
- Critical Miss explains the principle.
- Doctor Who fan Webcomic The 10 Doctors features all ten Doctors versus Dalek Tor (a Dalek version of the Doctor) in a battle for the Tenth Doctor's mind. Features Doctor quotes, Nine with a baseball bat, and a mega-merge Doctor who looks awesome.
- Superman going inside Brainiac 5's mind in the second Season Finale of Legion of Super Heroes stirs him to fight the brainwashing. There was also a Fusion Dance involved.
- Princess Tekla from Shadow Raiders, who fought Lamprey when the latter took over her body.
- The Teen Titans episode "Nevermore" takes place in Raven's head. It's a scary place.
- The Spectacular Spider-Man faced down the symbiote this way.
- The 90s X-Men cartoon was fond of this, and would make elaborate battles in a mindscape shaped by the combatants, making the grandest, most awesome (and trippy) affairs out of scenes that were basically two people glaring at each other in the comics. The most notable instances would be Professor Xavier versus the Shadow King, Jean Grey and Rogue versus Ms. Marvel's transplanted personality, and Professor Xavier going toe-to-toe with Dark Phoenix in Jean's mind (a duel only shown through a series of effects-laden panels in the comics).
- In an episode of the 90s' The Incredible Hulk cartoon, Banner was possessed by a demon; Green Hulk and Grey Hulk joined forces to kick him out of their shared body. Several episodes also showed the two Hulks fighting for control when Banner hulked out.
- In the Justice League episode "Only a Dream", the Leaguers have to engage in a fight with Dr. Destiny in their minds while Batman tracks him down in the real world.
- The symbiote asserts its dominance this way during its introduction in Spider-Man: The Animated Series, manifested as the symbiote and a giant Spider-Man costume struggling over Peter Parker. As surreal as it was, it was arguably one of the series' better fight scenes...
- The last episode of Disney's Aladdin: The Series to have Mozenrath in it ended with Mozenrath attempting to possess Aladdin's body after his own suffers total organ failure from overuse of dark magic (which turns out to apparently be the source of his interest in Aladdin through most of the series). After he stops being afraid, Aladdin uses the Power of Love to curbstomp Mozenrath's ass. This would have been a fitting end for the series Big Bad, but being a Disney cartoon, he gets better at the end to menace Agrabah another day.
- In The Fairly OddParents, Timmy and imaginary friend brought to life Gary battle in Timmy's mind.
- In Young Justice, Miss Martian and Psimon have a psychic battle of this sort. M'gann is invisible and Psimon is still psychically protected, making it difficult for the fight to be cut short mundanely.
- The last episode of Mighty Orbots has the heroes physically entering the body of their archenemy, the titanic supercomputer Umbra. This results in them finding themselves in his mindscape and having to fight off manifestations of his evil thoughts.
- Total Drama Revenge of the Island: After Scott clocks him with a club during "Grand Chef Auto" Mike has a showdown in his brain, with his 4 other personalities. He wins.
- In Teenage Mutant Ninja Turtles (2012), Splinter goes up against Rat King this way... and loses. It takes Leonardo and The Power of Love to get Splinter back.
- Gravity Falls has a variation where the battle takes place in a third party's mind. Gideon summons enigmatic 'dream demon' Bill Cipher to steal the code to Grunkle Stan's safe where he keeps the Mystery Shack's deed in exchange for helping Bill with "Something I've been working on. We'll work out the details later." Using a magic spell found in Journal 3, Dipper, Mabel, and Soos go after Bill in Stan's mind. After their interference causes Gideon to break off the deal, Bill and the three fight. Interestingly enough, neither side wins- Bill becomes impressed with the Pines Twins and Soos' cleverness and decides to let them live, and drops off a vague warning before vanishing.
- The episode of My Little Pony: Friendship Is Magic, "Do Princesses Dream Of Magic Sheep?" features an interesting example. Due to a nightmare inducing parasite infecting the Mane 6 that Luna created as The Penance for her actions as Nightmare Moon, Princess Luna has to go through a series of them to try and catch it. After failing to do so and it being released into the collective subconscious of Ponyville, Luna has to create a share dreamscape for the entire town so they can collectively fight it off, and each resident contributes part of their regular dreams to this shared realm. It's basically a city-wide battle taking place simultaneously in every resident's dreams and in Luna's.