Power causing insanity in literature.
- 20,000 Leagues Under the Sea subtly shows how Captain Nemo is slowly but surely losing his sanity by using the Nautilus as a Weapon of Mass Destruction: At the state of technology in 1869, a submarine could easily destroy any ship afloat without possibility of retaliation, so Nemo could easily cross the Moral Event Horizon once and again.
- In The Alchymist, one who goes the quick way to being "awakened" will not be able to comprehend the power, resulting in death.
- In All Our Yesterdays, future James started out wanting to use time travel to help people and save them, but he grew so far gone that he turned America into a police state and sent someone back in time to kill his own brother.
- Animorphs:
- In the main books, the Big Bad Visser Three is a General Failure with a strategy of brute force that's completely unsuited to the campaign of stealthy infiltration he's waging. Later, the prequel Chronicles books showed the younger Visser as a very capable Manipulative Bastard, exhibiting a thoughtfulness and cunning completely absent from his main incarnation. It becomes quite clear that once Esplin achieved his goal of becoming the only Andalite-Controller in the universe he let the power go to his "head" (it didn't help that his new host was a disgraced and mentally unstable ex-General Ripper either). It was all downhill for him from there.
- To a certain degree all Yeerks have the potential to succumb to this, as they are a Puppeteer Parasite race who incorporate elements of the Fusion Dance trope into their Grand Theft Me lifestyle. Literally every Yeerk character in the series is shown as taking on aspects of their host — Aftran in #19 has a somewhat childish attitude and mannerisms as her host is an actual child, the TV personality Yeerk in #35 has a bombastic Large Ham persona, and so on. The biggest smoking gun for this, though, is Visser Three's Dragon Taylor, a character who manages the very impressive feat of out-crazying her boss due to taking a severely traumatized and narcissistic teenager for her host while not being entirely mentally stable herself.
- The morphing ability used by the heroes is also a form of this, as every time they morph an animal they are interfaced with that animal's instincts. While certain animals have very mild instincts that are easily controlled, certain other animals are much harder to control (in the most extreme case, the kids almost lose their sentience entirely when morphing ants). It's not very predictable, either, even after they turn the learning curve and develop a greater understanding of morphing's rules and limits.
- The Black Company:
- The more powerful a wizard is, the more dangerous their quirks are, usually including being power-drunk and always including a lot of paranoia (the Lady even acknowledges the latter). The setting's strong aversion to Squishy Wizard is a treatise on the notion of individual power and the corruption of morality it engenders. Almost without exception, the powerful wizards of the setting are shown to be self-important monsters who have lost the ability to empathize with normal mortals; (the exceptions being low-powered casters like Goblin, One-Eye, Silent, and perhaps even Bomans) many of them even conducted wholesale slaughter in ages past to prevent the loss of their powers through invocation of their true name. They use their magics to make themselves Nigh Invulnerable, and The Limper spends most of book 5 illustrating how just how badly a Not Quite Dead Omnicidal Maniac can ruin things when given actual supernatural power. The Lady's redemption is coupled to her loss of her magical powers as a contrast to The Limper's rampage.
- The Limper provides an early example. He raises hell throughout most of The Books of the North, tries to backstab the Lady during The White Rose, and kills thousands out of pure malice during The Silver Spike. He is particularly vicious in the latter, when he is the most powerful sorcerer left on the continent and thus does not fear a reckoning.
- Soulcatcher gets more and more unhinged as the story goes on. Like the Limper, she is at her worst when there are no other sorcerers to oppose her.
- The Cobra Trilogy has people being made into Super Soldiers and adjusting to new strength, speed, and lasers in a matter of weeks. They're carefully screened beforehand; only the most emotionally stable ones actually become Cobras. Even so, a percent of them do not handle the transition well and develop something called a "Titan complex", the belief that one is so powerful that one is above normal laws and standards. Handing someone all that physical power at once, instead of having to acquire and use it in small increments, essentially sidesteps the usual adjustment mechanisms, according to the books. These people tend to decide that they know what's best and proceed to rebel until other Cobras either kill them or restrain them long enough to have the Super part downgraded. A major plot point is the main character, a Cobra himself, realizing that he has to help his colonies secede from the Dominion of Man and trying not to look like he's developed the complex.
- In The Cycle of Fire, the process of mastering fire powers involves experiencing being burnt alive. The trainee must get past the pain to understand the flames, which usually requires sacrificing all capacity for empathy, making them a sociopath.
- Magic users in The Dawnhounds have a form of Resurrective Immortality that means their patrons throw them back whenever they die. Each resurrection makes them more powerful, but also chips away at their sanity and personhood. It's implied that—after enough resurrections—they lose their grip on reality entirely and ascend out of the world.
- Poison-users in Dis Acedia eventually go insane, including the main character himself.
- Discworld:
- Witches make a study of defying this. The combination of magical power, a keen (and sometimes bruising) grasp of human psychology, and a solitary lifestyle tend to do weird things to their minds over time, so they take care to keep each other grounded and at least somewhat socially engaged so they don't "start cackling".
- In Thief of Time, Jeremy Clockson is the son of the anthropomorphic personification of time and implied to have inherited her subconscious ability to sense and measure the flow of time. It's made him a obsessive compulsive wreck who once attacked someone for setting their clock wrong, and even on his medicine, his new Igor comes to the conclusion that he's just as mad as any of his previous masters. His sort-of-brother, who inherited preternatural skill at manipulating time, seems to be much less crazy.
- Dragon and Damsel
- Edward accidentally reads a spell from a spellbook aloud. Being human and having no magic, he is driven mad for a short time as a side effect.
- Bernadette is able to use a dragon scale to cast spells...but ends up stuck in a loop with one spell, repeating it over and over as the magic is used up.
- A common trope in The Dresden Files, such as Hexenwulfen belts, the coins of the Order of the Blackened Denarians, and the mantle of the Winter Knight, as Harry finds out first-hand.
- The title character in Eden Green is a rationalist and amateur biologist, but once infected with an alien needle symbiote, its immortality (and increasing power) gradually pushes her toward the deep end.
- Evie Scelan: At the very least, most mages in the novels are highly paranoid. The title character aggressively cultivates a normal life to keep from going crazy herself.
- A core premise for Glory in the Thunder. Holding an Aspect greatly taxes mental fortitude, and gods are known for being more likely to go mad the longer they live. This means the immortals in particular tend to have left sanity behind a long time ago.
- In Gone, every villain (sans Zil) has awesome powers, and most of them are at some point insane from the revelation.
- Heart of Darkness critiques Britain's "liberal imperialism" in the form of Kurtz, who went insane because he has absolute power with no one to stop him.
- In the Hero.com series, along with its sister series Villain.net, when a Prime, someone born with powers that doesn't need to download them from the titular websites, downloads powers from them, it either causes insanity or death. There are also the six Core Powers, the original powers from which every other power in existence is only a weakened, mutated descendant of one or more of these powers, which can only be wielded by one person at a time (though 2 of them were divided into segments that different people could use at once, albeit in a weakened form). Of the six, 3 are known, a Time Master power, wielded by the villainous Lord Eon, power over life and death, and a Gravity Master power. The Core Powers can corrupt anyone without the strength of will to resist the lure of their sheer power, with only a few characters being immune.
- The Infected: The Infected gain superpowers but also a "first mode" or sort of personalized mental disorder. Some are existing disorders but worse and untreatable, several are emotional states amped up, like a man who can actually never stop being happy, or a person with crippling social anxiety.
- In The Invisible Man, the titular character starts out as a psychopath, but it gets much worse after he discovers the ability to turn himself invisible.
- The Iron Teeth: After his transformation, Blacknail can't control his thoughts and attacks Saeter. Only long training helps him. Still, the beast inside him is powerful and biding its time.
- Journey to Chaos: Breathing in the magical mist known as "Fog" will give the user tremendous boosts to both magical and physical abilities. It will also give them one heck of a Power High and then send them over the deep end into the monster mentality known as "Monsanity".
- In the Keys to the Kingdom series, Arthur begins to slowly get driven insane the more Keys he gets, and almost uses the power of the Keys to kill Denizens several times, but luckily manages to stop himself before he ever does.
- Jacen Solo in the Legacy of the Force novels seems to get crazier and crazier the more he falls to the Dark Side of the Force. He first justifies his actions as necessary sacrifices for the good of the galaxy, but by the end of Fury, he uses the Force to break an underling's neck for failing him. They don't call it The Dark Side for no reason. The same applies to Anakin/Vader and a host of other Expanded Universe characters.
- The One Ring in The Lord of the Rings slowly destroys the sanity of whatever schmuck has got a hold of it, first by making them obsessed with it and unable to let it come to harm, then tormenting and tempting them with visions of power they probably can't achieve, and finally devouring their mind. The other Nine Rings wrecked their bearers as well, giving them Age Without Youth until every moment of existence is an unbearable torture, and making them unable to disobey Sauron's commands even for an instant. The Seven probably aren't very safe either, though Dwarves seem to be mostly immune to the effects. Really, only the Three (which Sauron never touched) aren't liable to drive a wielder crazy, and that's only unless/until he regains the Ruling Ring.
- Malediction Trilogy: Many pure-blooded trolls can use very powerful magic and are also mentally unstable — probably due to 500 years of excessive inbreeding. The best example is young troll prince Roland, who is extremely powerful (like everyone in his family) and stark raving mad. His favorite pastime is to go out in the streets and brutally kill random mixed-blood trolls (who in this society are slaves without any rights).
- In Midnight by Dean Koontz, a rather twisted scientific genius has designed microchip-like spheres that augment a person's mental and physical abilities, but suppress all their emotions except fear, which produces some rather odd behavior on its own. Then the townspeople begin to discover that an accidental side-effect gives them mind-over-matter shapeshifting powers, and they promptly escape into forms in which their lack of emotions doesn't bother them — either animalistic creatures without the intelligence to notice, or cyborgs without any emotion at all. Everyone dies.
- Mistborn:
- Played straight and later justified in the third book with the Lord Ruler, a main villain.
- Also true for the Lord Ruler's Co-Dragons, the Steel Inquisitors. The Inquisitors use hemalurgy, a ghoulish form of magic that allows them to remove portions of someone else's lifeforce by killing them with a metal spike, trapping said life force in the spike, and then impaling themselves with said spike to acquire whatever power they stole. This makes them supremely powerful, but is in no way good for their long-term mental health. All the Inquisitors we see in the series are somewhat... homicidal. It doesn't help that hemalurgy provides an "in" for the series' Big Bad, the God of death and destruction called Ruin, to mess around with people's minds and in the case of people with several spikes like Inquisitors', outright control them.
- In Joe Haldeman's epistolary short story "More Than the Sum of His Parts"
, a lunar construction worker has half his body burned away when he gets caught in a jet of aluminum vapor, and undergoes massive reconstructive surgery, including robotic limbs and a prosthetic penis. Naturally he gets completely drunk with the power and capability of his new extremities. - My Work is Not Yet Done: Zig-Zagged by Frank Dominio, the Anti-Hero narrator of the short novel, who manages to go violently insane before he makes his From Nobody to Nightmare transition, then proceed to lose it even more whilst simultaneously gaining more and more control of his extremely scary superpowers.
- The Night Angel Trilogy: Dorian is one of the more powerful magicians in the book. He is immensely powerful in both the normal talent and the more addictive vir, and is said to be the best healer in living memory (living memory is a vague expression). But it is his prophetic gift that really gets to him. By the end, he is just sitting in a corner, laughing.
- The Night's Dawn Trilogy: Dexter Quinn is a magnificent example, taking back his own body from possession and using those powers to try to annihilate Earth.
- In Nine Goblins, all powerful wizards are certifiably insane. Keeping a firm grip on reality seems to check out when the ability to warp reality to your whim checks in.
- Anthony Burgess' One Hand Clapping is about a man with hyper-photographic memory, who uses this ability to become rich, and show his wife the life she deserves. She later finds out not being able to forget things has driven him insane, when he reveals his plan all along; to show her the good life, before ending both their lives in a suicide pact.
- In The Otherworld, this happens to necromancers and clairvoyants over time, and the more powerful they are, the faster their mental state degrades. Interestingly, necromancers can stave off the madness longer by using their powers rather than suppressing them.Good necromancers are plagued by demanding spirits. They're taught how to erect the mental ramparts but, over time, the cracks begin to show, and the best necromancers almost invariably are driven mad by late middle age. To maintain their sanity for as long as possible they must regularly relieve the pressure by lowering the gate and communicating with the spirit world. ... Clairvoyants also live with constant encroachments on their mental barricades, images and visions of other lives. When they lower the gate, though, it doesn't quite close properly, and gapes a little more each time.note
- Humans in An Outcast in Another World gain Levels much more quickly thanks to Fast Learner. Every time they level up, the euphoria of Leveling High makes them a little more aggressive and bloodthirsty.
- The Paradox Trilogy has a couple of examples. Maat, a powerful psychic, is said to have been driven mad by channeling more plasmex than any human was meant to contain. Symbionts are also prone to this, suffering mental instability as the price of the implants which grant them superhuman strength.
- The Perfect Run:
- This is usually what happens when a person drinks two or more Elixirs at once. Sure, they get both powers, but they become raging maniacs, constantly searching for more Elixirs to consume. This is on top of a number of horrific full-body mutations they suffer from.
- Also, to some extent, looping for a long time and a seeming inability to die is making Ryan gradually unhinged and impulsive, leading him to sometimes throw crude jokes at inappropriate times, break rules left and right, and intentionally offend his allies and enemies because It Amused Me.
- In Please Don't Tell My Parents You Believe Her, Penny (the "Meatbag" one) has figured out a way to invoke her powers on command through an ingested drug. However, it's making her progressively more violent and insane, and it's addictive.
- Pocket in the Sea: Lillenthal has shades of this in his character, but it's not clear if this is deliberate obfusification or genuine mental deterioration from living with a telepathic ability.
- In The Postman, the brutal survivalists/Holnists are led by General Macklin and his aides, who were pre-war experiments on creating soldiers with superhuman strength and speed. The government chose the most ruthless, intelligent, and efficient killers in its military, with foreseeable results when the US itself turned into an anarchistic warzone. Macklin is finally killed by George Powhatan, a later experiment of the same ilk, though with a nature-loving Neo-Hippie as subject.
- A Practical Guide to Evil: Catherine, the Sovereign of Moonless Night, effectively the Queen of Winter, becomes more strange and less humane as more she uses her powers: holding villainous monologues in the middle of a battle, grandiosely telling enemies secrets as intimidation, fighting after the reason for fighting disappeared, and using even more power all the while is rather far from sane.
- Michael Swanwick's short story "The Promise of God" is based on the premise that using magic gradually erodes a magician's moral sense until they no longer have any concept of right and wrong; magicians are kept in check by being assigned guardians whom they are trained to obey without question.
- This seems to be a side effect of becoming a hoshek in The Quest of the Unaligned, as infusing your soul with the fundamental essence of evil is not good for the mind. A lesser form of this effect seems to occur to Ruahkini. None too level-headed to begin with, becoming the second-most-powerful ruahk in the world infused him with a double portion of wind magic's flightiness and absent-mindedness.
- A key element of The Reckoners Trilogy. Epics started getting powers about 10 years before the first novel, and all end up falling somewhere between minor sociopaths to evil dictators. The series focuses on normal humans trying to kill powerful epics with their weaknesses, as well as learning more about the origin of Epic powers and why everyone with them seems to be insane. It turns out that with the exception of Transference Epics (a.k.a. Gifters), who give their powers away, any Epic who uses their powers will turn into a hateful, angry sociopath in minutes. Even people in close proximity are not immune to this — it's implied that Epic powers, even when Gifted, have a high probability of causing the same arrogant amorality in other people when used by them instead. One character alludes to a time when the police of his hometown joined with an Epic and "The good ones [left the force.] The bad ones stayed on, and they got worse." The main character, David, eventually discovers that the being who is secretly gifting Epic power is also what's causing them to turn people evil.
- Inverted in one issue of the German science fiction series Ren Dhark. At one point, the Terran world government decides to start a secret cyborg project with the help of a brilliant and highly ethical scientist. Thanks to very thorough advance evaluation and screening, the actual cyborgs turn out fine and become recurring supporting characters later on; instead, it's a candidate who gets turned down in the end (ironically precisely because he failed one of the psychological test scenarios) who goes a little Ax-Crazy as a result, devises a plan to destroy the entire fledgling institute, and almost succeeds.
- Schooled in Magic: Necromancers all eventually go mad with the amount of power they acquire from human sacrifice. The mechanics are revealed over the course of the books and fully explained in Past Tense. It's not necromancy itself, but too much mana for the human brain to handle, and the necromantic rite in particular fries the user's brain like an egg from the amount of power drawn. In the past, all magicians eventually went mad from channeling too much uncontrolled power, before the introduction of proper spellwork techniques.
- The Sister Verse and the Talons of Ruin has this in the powers granted by the Lord in White. All the characters in the first act completely lose their minds, and any darklings encountered are all wildly unstable.
- Soon I Will Be Invincible even gives this a medical name: "Malign Hypercognition Disorder".
- The Parshendi "forms of power" in The Stormlight Archive involve bonding with a sliver of the Platonic ideal of hatred. Not the best thing for one's mind. The strongest of these, 'The Fused', are affected badly enough that any who retain some sanity are considered qualified for leadership positions by default.
- Part of the backstory of Touch (2017) involves Earth's mages having to work together to stop an Eldritch Abomination. Part of the solution involved everyone with Super-Empowering abilities touching one guy who faced the thing in the final battle. He won, but he's not well, physically or mentally. His last coherent words were screaming for his mother, and he's visited daily by someone with Forced Sleep powers.
- In Vampire Academy, all Moroi spirit users are affected mentally by spirit-use, as it is drawn from themselves (as opposed to an element, such as air). And the more they use it, the worse it gets. It manifests itself differently in each individual: Lissa becomes extremely depressed at one point, which causes her cutting, Adrian has bipolar disorder, and Sonya Karp dealt with her insanity by turning Strigoi — although now that she's turned back, she seems to be okay, despite using spirit in most of her free time to find a Strigoi vaccine.
- In the Dale Brown book Warrior Class, Fursenko suspects that Yegorov is suffering from this, the power conferred on him by the Fisikous/Metyor-179 turning him from a mild-mannered and intelligent person to a seemingly Ax-Crazy Blood Knight.
- Saidin, the magic used by males in The Wheel of Time, is tainted by The Dark One, causing inevitable insanity in its users. As time progresses, one of the main characters begins to show the effects of this, becoming schizophrenic, moody, and temperamental; halfway through the series, he seems like a completely different person, though he is under a lot of pressure... The Forsaken also have access to what they call the True Power, an extremely addictive, evil flavor of magic that also has serious psychological consequences; most would only consider using it under dire need. Possibly exemplified best when some poor soul using Saidin breaks down after one day and starts screaming that there are spiders under his skin. It's also worth mentioning that Saidin use can bring about other lovely effects, such as rotting flesh. It is entirely random as to which will affect you first, when, and to what degree.
- Wizard of the Pigeons is based on a radical re-interpretation of this trope. Magic usually comes hand in hand with letting go of your previous life, memories, and basic perception of reality. Usually, the mage is so divorced from the outside world that he or she cannot hold down a job or personal relationship, and usually ends up living on the street. They also have to follow their own set of arbitrary rules and rituals, implicitly for the Placebotinum Effect. Cassie has been doing this since the Trojan War, and is so uninhibited by her environment that she can bend reality to her whim.
- Worm: Pretty much every single parahuman is an example to one extent or another, because a Traumatic Superpower Awakening is the only way of getting superpowers and it has to be a Despair Event Horizon level of trauma, so even the most well-adjusted capes have some nasty emotional baggage. Some of the more extreme examples are listed below.
- Burnscar becomes more unstable and violent the more she uses her power.
- Labyrinth's power over alternate universes is directly tied to her mental state, with it working better on days where she's less lucid and coherent.
- Scrub's power to erase select objects in his environment eventually renders him mute.
- Skitter's trigger event caused her to abruptly gain awareness of millions of insects. The shock of this was so severe it was assumed she'd had a psychotic break and she spent a week in a psych ward. After having Panacea mess with her brain, she gains the ability to control people, but her mind is gradually taken over by her shard.
- The Zones of Thought novel A Fire Upon the Deep has "godshatter", the Neural Implanting by Sufficiently Advanced Aliens of a massive Exposition Beam into a person's brain. It would probably be super helpful if the seemingly random jumble of information didn't turn the person into an erratic, drooling savant for most of the time.
