Sanity Slippage / Video Games

Sanity Slippage in video games.

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• Assassin's Creed: The first game had mentions of Subject 16, who committed suicide after excessively prolonged Animus sessions caused mental breakdown due to the "Bleeding Effect," where the Animus subject may gain their ancestor's abilities but end up being unable to mentally distinguish themselves from the ancestor, though Desmond only ends up gaining his ancestor Altaïr's Eagle Vision ability. In Assassin's Creed II this is deliberately invoked in an attempt to quickly train Desmond to become an Assassin, but along the way Desmond suffers visual hallucinations and experience (in his sleep) one of Altaïr's memories without being in the Animus. By Assassin's Creed: Brotherhood he's become an Animus-trained Assassin but the hallucinations have gotten more frequent, are now both visual and auditory (sight and sound) and may not even be from his ancestor Ezio's memories. On at least two occasions Desmond inadvertently refers to himself in the first-person when describing Ezio's actions, and later in the game an e-mail reveals that the other modern-day Assassins have heard Desmond screaming in his sleep.
  • Just to make it worse, Desmond is self-conscious of his own growing mental instability, at one point in Brotherhood wondering how long it'll be before he "starts painting symbols on the walls" (referencing Subject 16).
• Astra Hunter Zosma: In the postgame, one of the the superbosses, Cardboard Bob, went on vacation but got trapped in a void, causing him to go Mad From The Isolation. Even before that, his working conditions under Mr. Flap are still terrible, stressing him out further. The moment he sees Zosma and the blob companion, he attacks them thinking that he'll be allowed to go home if he wins.
• Batman: Arkham Series:
  • Over the course of the series, the Riddler gets hit with this pretty hard. With every game he tries harder to defeat you, and with every game he fails, cracking his fragile ego further and further until, by Arkham Knight, he's more ranting and aggressive than ever before.
  • The "Spirit of Arkham" audio file collectables found throughout Batman: Arkham Asylum detail Amadeus Arkham's slow devolution into insanity following the murder of his wife and daughter at the hands of one of his patients.
  • In Batman: Arkham Asylum, Scarecrow is insane, but not much more so than any other of Batman's rogues. After getting mauled and nearly killed by Killer Croc, he completely loses it and in Batman: Arkham Knight becomes arguably the biggest threat that Batman faces in the entire series.
  • In Batman: Arkham Knight, Batman is trying to prevent this, since he is mentally struggling with the Joker personality implanted in him by a tainted blood fusion; if he loses control, the Joker personality will completely take him over.
• Batman: The Telltale Series. While in most Batman stories, Harvey Dent immediately goes insane after becoming disfigured, in this game, he is initially unaffected by the experience, but slowly becomes paranoid and unstable as the new mayor of Gotham. What truly pushes him into becoming Two-Face is being affected by Lady Arkham's drug and discovering Bruce having an affair with his girlfriend, Selina Kyle. In fact, Dent loses his mind even without becoming disfigured if the player saves him.
• Bendy and the Ink Machine:
  • The players are introduced to voice actress Susie Campbell with her Chapter 2 audio log, in which she sounds like a Nice Gal excited about landing the role of Alice Angel. However, subsequent audio logs record her getting Lost in Character sometime before she became the murderous version of Alice Angel: In Chapter 3, she likes it when Joey calls her Alice. In Chapter 4, she calls herself Alice and accuses Joey of trying to double-cross an angel.
  • Players can first be introduced to Grant Cohen through his secret Chapter 3 audio log, in which he is complaining about Joey's spending habits and some big expensive secret project of his. In Chapter 4, we find his office.
• In BioShock anyone who is hooked on ADAM will slowly loses their sanity, as it destroys and rebuilds their physical and mental state. The best example is Dr. Steinman, in his audio diaries he becomes increasingly delusional, believing he's talking to the Greek goddess Aphrodite, and spends most of his time doing surgery on other splicers to create his version of what is beautiful.
  Steinman: An intruder?! He's ugly! Ugly! Ugly! UGLYYYYYYYY!
• Bloodborne has this happen to, well, basically everyone, but the most notable is Father Gascoigne, whose daughter mentions that they play a music box to get him to remember that he has a family. By the time you find him, he's become little more than a rabid animal hellbent on murdering everything in his path, quite possibly including his wife, even before he turns into a werewolf monster.
• This shows up in Borderlands through Patricia Tannis' logs. She starts out sane (if unenthusiastic) on Pandora and the combination of the world's environment and too much time alone pushes her from "Why do I have to be here?" to idle chitchat with someone pinned and dying under a stone pillar because she knows it's the last conversation she'll have with anyone for awhile to dating, then breaking up with, her audio recorder (they're still friends though). All this occurs prior to the events of the game and by the time you meet her she's...a bit off.
  • She also gives a dude named Crazy Earl an artifact to safeguard, and to seal the deal, some of her underwear as well. It was her idea too. Also, Baron Flynt punched her dog.
  • Tannis explains in the sequel how she became a bit nutty and how the bandits came to be on Pandora. Her and several people used to work for the Dahl corporation and they were sent to Pandora to mine for minerals and do research studies. After a while, the corporation ditched everyone and left them to fend for themselves, causing many people who were normal and had decent lives to slowly grow insane and become bandits. While Tannis simply became just plain weird, she admits that what Dahl did left her and many others broken.
  • Tiny Tina, world's deadliest 13 year old. The reason behind her total loss of sanity? Flesh Stick (yes, that's his name), sold her and her parents to Handsome Jack, for his Slag experimentation. Her mother gave her a grenade and taught her how to use. What next? Handsome Jack used them as guinea pigs. Seeing her parents mutate due to slag, Tiny Tina ran away after putting the grenade to a good use. Ever since, she went a bit nuts... BURN ALL THE BABIES!!!! Dummied Out audio files show Tiny Tina's descent into madness, but it was likely cut out for being a bit too disturbing since she's a pre-teen.
  • While Big Bad Handsome Jack started out evil (trapping your daughter in a small room for her entire life is not the action of a decent man), in Borderlands: The Pre-Sequel! and the "Get to Know Jack" sidequest in Borderlands 2, he's shown to have steadily degenerated from a reasonably controlled form of evil to the casually murderous, deeply self-obsessed version that gets pointed at the Vault Hunters in 2.
• Matthew Baker from Brothers in Arms follows this trope as the stress from losing squadmates and friends begins to pile up.
• This is a major gameplay element in Call of Cthulhu: Dark Corners of the Earth. The "hero" is slowly going insane due to all the Eldritch Abominations running around. This results in hallucinations, talking to himself, and hearing voices. The player can reduce the rate at which he goes insane by keeping him from being exposed to disturbing situations (this being a horror story based on the works of H.P. Lovecraft, that's easier said than done). If it gets too bad, the hero may attempt suicide and prompt a Nonstandard Game Over.
• Starts happening to the protagonist of Calmere Nightmare before long. According to the second map, the protagonist went insane at the end of the first map.
• Clive Barker's Undying: Journal entries show that this was inevitable for the Covenant siblings.
  "Can you hear the whispers, Jeremiah?"
• Confess My Love: Willie goes through one after enough endings had passed and the player gains access to the "Mutated Room". In this special ending, Liza turns into a demon and attempts to kill Willie. Back in the real world, Willie then gets flashbacks about the event, freaks out, and stabs Liza.
• The protagonist of The Consuming Shadow is already doubting from the beginning of the game if anything he experiences is real. It only gets worse from there as he sets out to fight Eldritch Abominations and other horrors.
• This is the result of the third week of CROSS†CHANNEL, the first week where Taichi knows time is looping and has more of his deep psychological issues surface. If it wasn't for this and the broadcast he makes at the end of that week, this treatment of Kiri would be rather hypocritical and unforgivable.
• In the Paradox Interactive Real-Time Strategy game Crusader Kings, characters can occasionally become Stressed. In itself, this only causes a slight stat hit, but if left unchecked, Stress can further worsen into Depression, Schizophrenia, or outright Insanity, and once one of those hits, that character is locked in a vicious spiral of stat decay, personality instability, and possibly even murderous sociopathy until he or she finally dies or gets "Locked Up for Good!" (which is effectively the same thing).
• This trope is EVERYWHERE in Cultist Simulator, and nigh anybody is at risk: your cultists as they're promoted, your pawns as they're over-promoted, occult authors when you get to their later volumes, Hunters you've shown powerful mysteries to... and of course the player character themselves, inevitably. But whether your descent into madness is careful and controlled or rapid and catastrophic is up to you.
  • Unusually for most Cosmic Horror games, sanity is not a single stat in and of itself. Instead, you've got Dread and Fascination, representing being consumed by despair or being so overwhelmed with rapturous visions you can't tell what's real. One can even be used to cancel the other out. Additionally, Dread and Fascination only kill you if you get three of them at once at the wrong time.
• Darkest Dungeon has this as a fundamental mechanic. Heroes can be stressed by their experiences in the dungeons, including encountering disturbing objects, being hit by traps, and especially the horrifying and nightmarish attacks many monsters unleash on them. If their stress grows too high, their Resolve will be tested. If they fail, they will gain an Affliction, in which they start becoming mentally unstable and begin lashing out at their allies, wailing in terror or hopelessness, or babbling irrationally. If they succeed at the test, however, they will become Virtuous, becoming tougher and stronger and supporting their allies.
• All over Dead Space. Alongside the Necromorphs, The Markers cause hallucinations, homicidal and suicidal ideation, paranoia, and a whole host of other pleasant symptoms. Most characters in the series are affect at least to some degree. Including protagonist Isaac Clarke, whose deteriorating mental state was The Reveal in the original game and a major plot element in Dead Space 2, where he had to find a way to stop his insanity before it made him kill himself.
• In Digimon Survive, This can occasionally happen. The first of these to happen is Ryo, who steadily gets more and more unstable throughout chapter 3, believing he and the other children are in the afterlife. and if not snapped out of it (which is impossible on a first playthrough), results in him being the first of the party to die. Second is Shuuji, who, after being hit by Arukenimon's hallucinogenic fog, grows more and more unstable throughout Chapter 5. Unless Ryo survived, this causes him to trigger Lopmon's dark evolution into Wendigomon, directly resulting in his death. Lastly, after Chapter 8's Route Split, one of two characters can suffer this depending on the route. The Wrathful Route has Aoi, who undergoes this once Saki dies, with the resulting mental breakdown eventually resulting in her causing a Dark Evolution and Biomerge with Labramon to form Plutomon, the route's Final Boss, which, naturally, results in the rest of the party being forced to kill Aoi, as she is too far gone at that point to be reasoned with. In the Harmonious Route, this instead falls on Kaito, who slips further and further into insanity after the death of Miu, resulting in him being manipulated by Piedmon to fuse into Boltboutamon, the route's Final Boss, for enough power to kill The Master. And while Kaito is originally in control of the fusion, his hatred eventually wanes, allowing Piedmon to retake control, which spells the end for Kaito. Thankfully, No such thing happens in the Moral or Truthful routes.
• Donkey Kong 64: King K. Rool shows this. After being defeated three games in a row he goes as far as to attempt to destroy DK Island with his "Blast-O-Matic", even going so far as to put his and his own minions' lives in danger just to fire it.
• In Don't Starve, your character has a Sanity Meter that slowly goes down if you neglect it. If it gets low enough, you start seeing flickering visions of shadowy monsters. Let it drop even lower, and various crazy things happen: the wild rabbits roaming the land become replaced with monsters made of hair called Beardlings, shadowy hands might reach out to snuff out your campfire at night as an Ominous Music Box Tune plays, and the shadowy monsters you see become more and more real until they come to life and try to kill you.
• Dragon Age II: Anders slowly gets driven mad by Justice over the course of the game, slipping from strong supporter of the mages to crazy extremist, becoming completely consumed with his cause. His views become so extreme that you're either with his cause or an enemy to it. His madness culminates when he blows up the Chantry to force a confrontation between the mages and Templars.
• The Harran virus in Dying Light first causes seizures, then increasingly vivid hallucinations that rapidly take on a terrifying tone if the uninfected are unable to get their supply of Antizin on time. If it's allowed to progress past that, zombification is the inevitable (and irreversible) result.
• The Elder Scrolls III: Morrowind:
  • The Sleepers, otherwise normal people who've been influenced by Dagoth Ur's Psychic Dreams start out babbling about Dagoth's return and the rise of the Sixth House. After a certain point in the main quest, they will turn hostile and start attacking the player.
  • Dagoth Ur and the Tribunal all suffer from sanity slippage to varying degrees as a side-effect of becoming Gods through the power of the Heart of Lorkhan. Dagoth Ur has it the worst, since he was far less restrained in his consumption of the heart's power. Of the Tribunal, only Almalexia exhibits any obvious signs of insanity, though it is implied that Vivec and Sotha Sil would have eventually suffered the same fate.
• Eternal Darkness has this as one of its main gameplay mechanics with a "sanity gauge" that drops whenever enemies are encountered. Once it gets low, the really weird shit kicks in.
  "This...isn't...really happening!"
• In Fallen London you can start suffering from nightmares. As nightmares increase your character starts being unable to tell the difference between their dreams and reality, eventually driving you completely insane and resulting in you being taken to the Royal Bethlehem Hotel. Fortunately this is reversible.
  • There is also a certain storylet called Seeking Mr Eaten's Name. At first this simply manifests as a minor Horror Hunger, but as time and the story go on your character becomes increasingly insane and self-destructive. This includes doing things like baking your own face into a pie, or eating your own teeth, or rendering a candle out of your own body fat. Even compared to the general insanity of the Neath, Seekers are bad.
• Final Fantasy:
  • Kefka in Final Fantasy VI. He was once a general, but he starts disobeying orders and has lost his rank by the time the game's narrative begins. And he just keeps getting worse from there, culminating in the development of a massive god complex and an urge to destroy everything.
  • Edda in Final Fantasy XIV starts out as a simple, if timid, healer in a group of adventurers looking to make money and a name for themselves. Her boyfriend, who is the party's tank, constantly belittles her subpar healing skills and the others make fun of her for having to rely on potions to heal. When Edda's boyfriend runs ahead of the group in a dungeon, his act of recklessness gets him killed, but the others blame Edda for his death (for not keeping up to heal him). One would show sympathy towards the poor girl, but then her former party reveals that she's been carrying her boyfriend's severed head around. From there, she goes completely nuts by using dark magic to revive her boyfriend as a monster and invites the player character to her "wedding" in order to use their body as a vessel for her revived lover.
    • The tooltip for the debuff caused by the Dark Knight's Scourge in Final Fantasy XIV is "Sanity is slipping, causing Damage Over Time."
• Fire Emblem: Across the series, this has been a significant element regarding the dragons. As the millennia pass, they succumb to what's called "degeneration" and begin to slip further and further into insanity, losing all reason with some even becoming completely feral. This is so prominent that this is seen in worlds that are completely separate from one another.
  • In Fire Emblem: Shadow Dragon & the Blade of Light, the Earth Dragons refused to seal their power and become Manaketes, causing them to all degenerate until there none left with any semblance of humanity. Fear of this also led to Tiki being sealed away, since her immense power could have destroyed the entire continent, especially if she were to degenerate prematurely.
  • Fire Emblem Gaiden has Mila and Duma, the dragon gods of Zofia and Rigel respectively. Duma by the time of the game has gone completely mad, driving his followers mad and being consumed by a desire for power. While Mila seems to have avoided this, she allows her people to grow greedy while the land fails and shows a mad blood lust when the Rigelian Emperor comes to kill her.
  • Fire Emblem Fates
    • The main antagonist Anankos was once a kind soul who helped humanity flourish and even developed a magic song to stave off his insanity, however after he accidentally destroyed a forest humans attacked him and drove him into hiding, where he once again lost control and killed the one person who still believed in him. In a last ditch effort he tore his soul in half to preserve what sanity he had, only for the other half to fully dive off the deep end. Eventually the mad half killed the sane half, though not before the sane half set into motion events that could stop him when the time came.
    • On the Conquest route, Takumi starts off reasonable, but over the course of the game becomes increasingly violent and obsessed with killing Corrin for their betrayal. This is because Anankos is amplifying his hatred to turn him into a new vessel. After beating him at the Great Wall of Suzanoh, Takumi commits what is implied to be Psychic-Assisted Suicide so that Anankos can fully possess him. As the Final Boss, he's nothing more than a completely insane killing machine only capable of ranting and screaming about how much he hates Corrin and Nohr and trying to kill them all.
  • Fire Emblem: Three Houses:
    • Dimitri starts off as kindhearted and chivalrous, but underneath he's dealing with a lot of issues due to his Survivor's Guilt over the Tragedy of Duscur. Over the course of Part I, his self-control erodes as he faces Those Who Slither In the Dark and the Flame Emperor, and the revelation that said Flame Emperor is his stepsister and childhood friend Edelgard sends him off the deep end proper. When he returns in Part II on all routes save Crimson Flower, he's become a madman completely obsessed with revenge and uncaring about the kingdom he is supposed to be protecting. On the Silver Snow and Verdant Wind routes, he gets himself pointlessly killed at Gronder; on the Azure Moon route, it takes a lot of guidance from Byleth, but he eventually recovers; on the Crimson Flower route, Rhea keeps him in check and he doesn't fall as far as he does on the other routes.
    • Rhea starts off as a kind and patient holy woman, albeit with a dangerous temper. In most routes, she stays that way, but in the Crimson Flower route, constant pressure and pressing of her Trauma Button leads her to snap and become a bloodthirsty villain, to the point of eventually ordering an entire city to be burned down in an attempt to kill Byleth and Edelgard.
• Sergeant Michael Becket of F.E.A.R. 2. A combination of Alma's Mind Rape powers, her actually raping him, and being held captive by Armacham for nine months while being continuously tested and experimented on has driven him gradually insane by the time F.3.A.R. rolls around.
• Salvatore Leone from Grand Theft Auto comes off as a friendly, if ruthless man in Grand Theft Auto III, only to try and have Claude killed because he suddenly becomes convinced Claude's a spy. Grand Theft Auto: Liberty City Stories shows that he had fits of extreme paranoia before this, one time nearly blowing Toni's head off while accusing him of scheming behind his back. Grand Theft Auto: San Andreas reveals that this extreme paranoia was caused by CJ playing him (and pretty much every other faction that was involved) for a fool in the Las Venturas casino heist arc.
• In Hotline Miami, Jacket begins the game as a (relatively) sane person, but as the game continues, his mass-murdering sprees begin to take a serious toll on his mental wellbeing. The shops that he visits after completing each chapter gradually become more and more surreal and disjointed, with the horrifically maimed corpses of his victims appearing both in his home and out in public, the game's signature Sensory Abuse becoming spliced with quick jolts of television static, and the dialogue becoming increasingly Mind Screw-y.
  • Carl (from a fan-made comic which was endorsed as canon by the game's developers) is implied to be suffering from one of these as well. It's never revealed if his attempts to find out the truth behind the mysterious phone-calls drove his mind off the edge, or if he was simply always like that, but regardless, he is clearly not a very stable person. Carl is introduced in the comic speaking into an undialed pay telephone, apparently believing that 50 Blessings can hear him, and he continues to talk even after he has abandoned the phone and walked away. And that isn't even going into his absurd plan to break into the mobster-controlled nightclub.
• All three of the main characters in Ib can experience this. While Ib is on the outside the calmest of the trio, she doesn't really handle the gallery well. She hallucinates constantly, seeing bunnies when she looks at dolls, seeing images of herself hanged, etc. Mary displays a bit of neediness from the get-go. It turns out she is already unhinged, and can become even more so depending on how her companions interact with her and the gallery in general. Garry is probably the sanest of the three and only starts slipping mentally if the player lets him. If Garry fails the doll room event, he gets brainwashed by the dolls. Generally a good slap on the face is all it takes to bring him back, but if he's been kicking over a lot of artworks before that point, the damage to his mind is permanent.
• The title character of Iji can experience this, depending on player actions/inactions. She becomes increasingly desperate and maniacal if her body count increases rapidly (going from crying "I'm sorry!" to those she kills to shouting "DIE!"). She also swiftly goes completely unhinged if Dan is killed, even the final boss shows sympathy for her state.
• Injustice: Gods Among Us: In an alternate version of the DC Universe, after being tricked into killing his wife Lois Lane and nuking Metropolis by The Joker, Superman establishes a dictatorship on Earth. He Can't Take Criticism by responding with outright violence at times, ranting about how "ungrateful" people are towards his rule, and blaming others for his misfortunes. He even kills two of his own allies when they realize how far he's fallen, and threatens to destroy Metropolis and Gotham when people began revolting. Regime Superman even develops an obsession on Multiverse Lois when told about it, planning to forcefully take her as his bride even if she won't like it and kill Multiverse Superman. By the end of the game, he's much worse than the insane clown he killed earlier.
• Jim slowly goes mad as Jim's Computer goes on as his hallucinations and paranoia worsen, leading to the point that he is too scared of what he thinks is after him that he kills himself.
• Pit of all people starts to go crazy in Kid Icarus: Uprising. In Chapter 23, he gets eaten by Hades after the 3 Sacred Treasures are destroyed in front of him. When he's eaten, he's isolated from the outside world and can't get into contact with Palutena. Only Hades can talk to him from the inside and constantly taunts him the whole dungeon. It gets to the point where Pit starts talking to himself and acting like he's going crazy. Then there's chapters 18-21.
• Knights of the Old Republic II: The Sith Lords: This is the entire plot arc for Atris. Before the events of the game she tried a gambit to try and lure the Sith out of hiding. It backfired horribly, killing nearly all the remaining Jedi in the galaxy. As a result the ex Jedi Council member is cooped up on a remote planet with her handmaidens desperately trying to convince herself she was in the right, and that she can till save the Jedi. Furthermore she is convinced you are the real villain no matter what you say, or do.
  
  Over the game's length she starts to crack even more, no thanks to Kreia's influence and the Sith artefacts she has gathered, but surprisingly if you are restrained in your final meeting with her she shows signs of recovery and there's a "Ray of Hope" Ending for her
• Double subverted with Zant from The Legend of Zelda: Twilight Princess is normally calm and collected, but this is merely a facade, as he's actually completely nuts. During his boss battle, he reveals his true colors, but becomes even more insane as the battle goes on, until he goes apeshit and is reduced to a screaming, maniacal wreck.
• Middle-earth: Shadow of War lets you do this to Uruks by "Shaming" them: there is a chance while Shaming that the Uruk will become "Deranged" and have their mind snap in two, permanently altering their personality. It is also likely that the Uruk may become a "Maniac" and, even with their mind melted, Come Back Strong.
• Route C in NieR: Automata has a major case of this for 9S. In-between learning the Awful Truth about YoRHa and the Council of Humanity, the destruction of the Bunker and the corruption of his fellow YoRHa units, and witnessing 2B's Mercy Kill at A2's hands, he slowly goes insane with grief and rage as he resolves to the destroy the machine lifeforms once and for all and kill A2. By the time the Terminals start screwing with him by attacking him with copies of 2B, his response is to go Laughing Mad and start gleefully hacking them apart.
• In the Persona series, this happens to the public especially in the endgame. The changes are often highly noticable and outright terrifying.
  • At the January of Persona 3, people in Tatsumi Port Island began saying insane things, a few were in catatonic depression, and Strega leaflets and graffiti can be seen all over the city with nobody to pick on them.
  • At the December of Persona 4, the town gets surrounded by fog and the background music was replaced by some eerie noise, and the townsfolk began saying insane things such as "healing cults."
  • This is extremely obvious in Persona 5. After you get Futaba to join you, you will notice that people treated the Phantom Thieves as godly existences, but after you beat Okumura, since they thought that you were killing him, the Phantom Thieves automatically turn into Hate Sinks for everyone and it only goes worse after beating Shido. Near the end of the game, even if Mementos already bleeds into the real world, nobody but your Confidants can notice it.
    • Goro Akechi in Persona 5 is eerily calm when you confront him in Shido's Palace. However, once beat his first phase, he enters a Villainous Breakdown, transforms into the Black Mask and attacks you while screaming obscenities. Interestingly, he really fights like that as the Black Mask and even if in that confrontation he did use the berserk ability on himself, it didn't make much of a difference.
    • Actually Exaggerated in Persona 5 Strikers. While the public still goes insane thanks to supernatural influences with the final one being the worst, the public is rendered insane all at once, with a few being shown on screen and in other cases, the whole city or prefecture has been driven insane before the events of the game occur.
  • Persona Q2: New Cinema Labyrinth:
    • Yosukesaurus in the second movie is generally friendly, but he felt powerless about not being able to lead the Herbivores into resisting the Carnivores. When he led the other Herbivores into a "paradise" which was revealed to be a dead-end clearing that just makes them Carnivore fodder, all of the Herbivores voted to ostracize him and kick him out. He doesn't want to and they force him to attack the party because humans wrote the book depicting "paradise." He gets mind broken piece by piece, finally turning into a carnivorous dinosaur himself to mercilessly attack the party.
    • While Hikari was nothing more than a depressed wreck at the start of the game, she used to be quite sane when she was young; Even when she was wrongly blamed for poisoning the class rabbit by her primary school teacher or ostracized by her secondary school friends for having a different opinion on how Miyuki should be treated, she can still talk to her father with a straight face. However, after her relatives denied her worth, all hell breaks loose; She just collapsed in a fit of depression and self-loathing and closed herself off in her room so she would be "normal" under the emotional premise that everyone hated her for being different. Her father then accidentally triggered her Trauma Button by asking her a question in the exact phrasing as everyone said before they flip out as a concern for her mental health. Needless to say, he was her only beacon of hope, so she snapped and became the Nervous Wreck encountered in the theater.
• Pikmin: For the most part, Louie starts Pikmin 2 off as a somewhat quiet, but still decent worker. But after he accidently is left behind on the planet, he goes a bit off the deep end by choosing to hide in the the final level of the game and it's heavily implied he was controlling the Final Boss. By the time Pikmin 3 rolls around, the only word he can say is food and he manages to get himself stuck on the planet again.
• (Some of) The characters in Psychonauts whose minds you enter, but especially the ones in the asylum levels.
  • Fred is a particularly striking case, starting out as an asylum staff member and becoming one of the very patients they treat.
  • One of the nice things about this game is that you invert the process for a few characters. By helping them confront deep-buried issues and work through problems they get some of their lives back.
• Dutch van der Linde goes mad throughout the course of Red Dead Redemption II. He starts the game as a charismatic leader but goes off the deep end as his gang gets into worse and worse straits, compounded by his own bad decision making. Some characters note that he’d been acting differently since before the game started, like outright murdering a woman. However, whether or not he truly went mad or if he was always that way and just didn’t have the facilities to hide it anymore is left open to interpretation. Even in-game, characters have different theories about what exactly happened to him.
  • This also appears to happen to Bill Williamson between the second and first games. In II, he's gruff and socially inept but still has a moral compass and is loyal to his friends. Twelve years later, he's turned into a complete psychopath who commits heinous crimes without batting an eye. A campfire conversation in II reveals that he watched his father go insane when he was a child, which raises the possibility that mental illness runs in his family.
  • Played for laughs with the Stranger, Nigel, who can be found around the game constantly asking for his friend Gavin. Years later in the Epilogue when John finds him, he's a shaggy, unkempt mess who's still been looking for him all these years to the point he's forgotten what he even looks like, but can't stop.
• In Schizophrenzy, you play Private Investigator John K. Facey — a severe schizophrenic. Your sanity is represented by a sort of "health meter" and is constantly decreasing, with only your medication keeping you from going completely over the edge. Of course, even fully medicated you perceive yourself as walking on walls and hallucinate bizarre creatures.
• A common occurrence within The Secret World, given that mind-warping magics and Lovecraftian horrors abound throughout the setting.
  • Anyone exposed to the Filth undergoes a gradual mental breakdown before the physical mutations set in. Beginning with hideous nightmares, suffers may experience symptoms including (but not limited to) catatonia, hallucinations, aphasia, paranoid delusions, violent episodes and shockingly irrational behavior. For good measure, many develop an unhealthy obsession with the Filth, and sometimes even the desire to serve the Dreamers directly, ending with their personalities seemingly being subsumed by their new masters. In particular, Dr Schreber's journals unintentionally charted his degeneration from cold-hearted professional to a delirious Filth-obsessed lunatic sabotaging his own project from within.
  • Deliberately microdosing himself with the Filth in order to build up an immunity to the nastier effects, Dr Klein ended up with a far more subdued case of this. Among other things, he believed that he was able to catch his shadow from pouncing on him by turning his head fast enough, ranted wildly about parasite-infected snails and degenerated into psychopathic megalomania... but other than that, he was almost perfectly lucid. In fact, he actually ends up being the second-most coherent of the Dreamers' minions — the first being the Black Signal.
  • Members of the Fear Nothing Foundation experience this over time as the cult's brainwashing methods start to eat away at their sense of self; in one undelivered letter to his parents, one hapless member admits to spending half an hour crying and banging his head against a wall, all because one of the counselors gently rebuked him for shaving the wrong way. In the next message, the formerly-hysterical writer has been completely indoctrinated and is willing to face mass-suicide with a smile on his face.
  • On Solomon Island, anyone who visits Atlantic Island Park begins to experience this: workers experienced disturbing impulses and stimuli while building the place, and as The Park explains, one was so distorted by his time there that he refused to let his girlfriend see him until he'd recovered from whatever he'd experienced there — and it may have even resulted in him having committed suicide. Meanwhile, a park worker playing the part of Chad the Chipmunk began to degenerate from alcoholism to utter obsession with his mascot suit, taking it home with him, declining to clean it, and even refusing to take it off; he also developed a taste for ice-carving — and finished up his time at the park by carving a teenager's eyeball out. Most notably of all, Lorraine begins to experience this herself as she delves deeper into the abandoned park, her love for Callum being gradually twisted out of shape into a demented, possessive obsession that arcs wildly between unhealthily doting on him and despising him with all her heart. It so happens that the reason for this is because the park's creator Nathaniel Winter was actually harvesting the emotions of the visitors - specifically their joy and happiness.
• The Shadow Hearts games, along with the usual HP and MP gauges, also feature a Sanity Gauge, as the characters are constantly fighting horrific and twisted abominations. If the Sanity of any character slips below zero, the background music changes and the character goes berserk, attacking everything around them.
• Shin Megami Tensei: Devil Survivor has an odd example of an AI apparently undergoing this. The Laplace Mail starts out giving news from the future, but as the game wears on (and the protagonists repeatedly prevent its predictions from coming true), it starts to get glitchier and glitchier, first capitalizing random letters and eventually adding in weird symbols in place of them, changing its "Have a nice day" ending to "Have a nice death", and finally spitting out an error message and discontinuing all together.
• Sid Meier's Alpha Centauri: If you're really kicking the crap out of another faction and refuse to accept their surrender, they send you increasingly-crazy messages until you kill them or otherwise stop the war.
• Happens to Eddie in Silent Hill 2. He starts off as a scared yet lazy kid, but later on he kills a couple of men and threatens to kill James. In truth, he's been crazy all along, just like James.
• In The Sims 2, if a Sim's aspiration meter is very low, they'll start doing crazy stuff related to their Aspiration:
  • A Romance Sim will try to dance with a mop...
  • A Popularity Sim will start talking to a puppet made out of a plastic cup...
  • A Family Sim will cuddle a flour sack with a face drawn on it like it was a real baby...
  • A Knowledge Sim will start talking to a volleyball with a face painted on it wearing a mortarboard...
  • A Pleasure Sim will put a lampshade on their head and dance around like an idiot...
  • And a Fortune Sim will go out on the street and beg for money.
  • If a Sims' Aspiration Meter bottoms out completely, they will collapse on the ground babbling. Then a therapist (who is only visible when that sim is selected) will appear and talk to them for a while, moving their aspiration meter back up one level.
• The entirety of Sonic Forces is caused because of this: The creature who would become Infinite flipped his lid after Shadow effortlessly defeated him, called him weak and to never show his face to him again before disappearing. He did not take it well, leading him to be used by Eggman as his weapon.
• Captain Martin Walker, the main character of Spec Ops: The Line, steadily loses his sanity throughout the course of the story, even more so after he and his squad inadvertently kill dozens of innocent civilians with white phosphorous. He starts to hallucinate more and more as time goes on and even imagines entire conversations with Colonel Konrad, who at the end is revealed to have been Dead All Along, to somehow rationalize that he was forced into his actions. This extends to his behavior in gameplay, as his combat finishers go from being quick and pragmatic to over-the-top brutal, and his dialogue gradually devolves from professional military expressions to loud, insane Battle Cries consisting mostly of angry rambling and cursing at his enemies.
• Fentible of Starship Titanic suffers for these occasional, usually in mid conversation. The end result is mostly rudeness and forgetfulness. Thankfully he can be reset.
• Star Wars: The Old Republic:
  • In a somewhat stranger example, Revan After three hundred years of being trapped in stasis and mind raped by the Sith Emperor, (all the while subtly influencing him NOT to attack the Republic) he's broken out by a strike team..... Only to immediately go to one of the remaining Star Forges in the galaxy (you know, the Eldritch Location he spent the better part of the first game trying to destroy?) and attempts to build a robotic army that will wipe out all those in the galaxy that contain even a trace of the Sith gene in them-incidentally 97.8% of the Imperial population. Not that, given his situation, this isn't slightly justified.
  • After the Foundry is seized by an imperial strike team and Revan pulls a Villain: Exit, Stage Left. He returns in Shadow of Revan (pulling an army out of his ass in the process) after deciding "Screw it; let's kill everyone" promptly declares war on both the Empire (reasonable) and the Republic (less so). It's not like he was trying to save the galaxy before... oh wait.
• In The Suicide of Rachel Foster, Signs of insanity appear on Nichole near the end of the game. The Reveal also tells that Irving has been mad from the beginning, but he had somehow managed to hide it well.
• This plays out in reverse in Time Fcuk. The protagonist is a Heroic Mime, but due to the unusual nature of time and space in the game, he often gets radio messages from his past and future self. In the beginning, you're getting messages from what seem to be several future selves, ranging from a Perky Goth to a Conspiracy Theorist to someone who's flat-out hallucinating. Towards the end, you can hear his early messages, when he was The Everyman— making it scarier, now that you know exactly how he'll be broken.
• Trenches (2021): The soldier starts losing his mind over the course of the game, with his vision blurring, hearing babies crying, and at one point his vision going red and seeing corpses strewn across the ground.
• Vampire: The Masquerade - Bloodlines featured a quest in which one has to "cleanse" a haunted hotel (much akin to The Shining). Upon finding the diary of a woman whose ghost now lives in the house, one can read her tale of how her husband experienced one of these inspired by romantic jealousy, culminating in him murdering her and her two children and killing himself.

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