For some, the temptation of god-like power becomes too great. However, this type of power was not meant for mere mortals to wield. The prospect of cramming that much power into a mortal vessel destroys the recipient's mind, leaving him an empty shell of a man with unlimited power but the mental faculties of a half-wit child, or worse, a feral animal.
Conversely, some gods or other powerful entities may grow beyond their bounds, steadily losing their sense and reason as their power grows, in the end leaving them nothing more than creatures based solely on instinct, with untold powers behind them. This sort of tale is common in a Cosmic Horror Story: A monster can be even more frightening if there's no point behind his actions, just mindless aggression, rage, or even simple curiosity.
- AKIRA: This is said to have happened to Akira in the manga series. The child does seem to have no real will or personality of his own.
- In Dragon Ball Super, Fusion Zamasu's One-Winged Angel form is an Eldritch Abomination and the most powerful villain in the series yet, however at the cost of what intellect and little sanity he had left, becoming a mindless force of destruction. Given he's assimilated the future timeline and has begun to leak into other timelines, him being this trope is a good thing as the only way the heroes managed to beat him is summoning Zen'o and had no way to fight what he'd become.
- Berserk: The Godhand don't qualify, being highly intelligent (unfortunately). However, when a would-be usurper (Emperor Ganishka) attempts to transcend Apostle-dom, he instead becomes this trope (also unfortunately).
- Towards the end of Naruto, Tobi becomes the host of the Ten-Tailed Beast, reducing him to this state. It gets to the point where he cannot remember his own name. Only by holding on to the memory of his dead comrade from his childhood does he regain his sanity.
- Digimon Adventure: After Myotismon is defeated and killed by the DigiDestined, his bats familiars consume his remaining underlings and fusion with his mask, allowing the vampire digimon to be reborn into his Mega form, VenomMyostismon. Unfortunately, VenomMyostismon is nothing but a mindless and feral beast whose only objective is to destroy and devour everything in his path.
- In one Doctor Strange arc, Strange destroyed a primordial entity of Chaos by assuming its power—and then killing himself. This led to him briefly becoming an all-powerful transcendent being with no ego or identity. Ironically, it was one of Strange's old enemies who dragged him back into the "illusion" of self.
- In the Preacher comic series, Jesse Custer was the host for Genesis, a potentially all-powerful newborn spirit that had no sense of individual will.
- ANYONE in Marvel Comics that has Intelligence of 1, but the rest of stats in Power Grid maxed out.
- Larfleeze from Green Lantern is deranged Idiot Savant who's only concern is stealing shiny things. He's also the only Orange Lantern, meaning he has sole access to all of the Orange Light's power. This makes him one of the most powerful ring wielders in the universe, a borderline Physical God in comparison to The Chosen Many that compromise the other Lantern Corps. Fortunately for everyone else, his insanity and kleptomania means that he prefers to hide himself away and guard his loot rather than cause havoc.
- Pony POV Series has Azerhorse, based on Lovecraft's Azathoth. The Truly Single Parent of its "family", it and its spawn are the embodiments of the fears of the unknown, existing so mortals don't progress recklessly. Most of the time, it does not speak or act, with its children created by accident. It is not good or evil. It doing anything with intention is enough to shock even the Elders. The first time it does is it to let its children know how utterly royally clopped off it is for disgracing the family for letting themselves be beat and ruining the whole point of them be unknowing entities (the only ones it wasn't annoyed with were Fillimon and Ponythulhu) and thus banished them from the unvierse for several billions of years. The second time is even more shocking, since it lacks the explanation of the first reason... agreeing to resurrect Button Mash. Why? Who knows? Perhaps it felt like doing someting nice.
- The writings of occultist Aleister Crowley describe a demon named Choronzon who guards the Abyss. Choronzon behaves chaotically, babbles nonsense, and has no true sense of self, but it's also highly dangerous when summoned.
- The Deathstalker books by Simon R. Green features an infant with the power to annihilate whole stars with a thought.
- The Divine Comedy:
- Although the giant Nimrod retains all his earthly size and strength while in Hell, he is the only soul who speaks humanity's original, pre-Babel tongue. As such, the world's greatest hunter is left only able to speak nonsense and unable to understand any other language as anything but babel.
- Satan's arm is larger than the giants and reigns as emperor of Hell, but he is too consumed by his hatred for God to notice that he is the one creating the bitter cold trapping him in the bottom of the Ninth Circle. Even worse, he seems to have lost all ability to communicate and reduced his mouths to killing machines used to rip apart fellow traitors in a vain attempt to express his misery.
- In the Enemy Lines two-parter, Lord Nyax is this. He's a Dark Jedi who was badly brain-damaged in a fight he'd had with another Dark Jedi, and was only saved because his mother was there to put him in a form of stasis. He was given treatment to boost his physical and Force-wielding abilities, but he woke up before the personality and mental restoration/improvements that his mother had planned could be implemented. As a result, he's an extremely powerful opponent with few weaknesses, but an extremely simplistic mindset and set of motivations. And then he successfully gains access to a wellspring of the Force.
- Azathoth from H.P. Lovecraft's work is known among Lovecraft fans as the Blind Idiot God. He created reality by accident, and will be equally oblivious when he destroys it. He's really more of a metaphor for primal chaos than a being in his own right, though; he's quite literally mindless.
- In Shadows of the Apt, this is the true nature of the Worm; an immensely ancient and powerful thing that has no sentience to speak of and desires nothing but to feed and assimilate. The creature's sheer stupidity is so powerful it can actually affect other people; magicians exposed to it, or even its minions, will completely forget how to cast spells, and Apt will lose the knowledge of how their technology works. The Worm doesn't understand magic or science, and its influence makes sure nobody else does either. Ultimately, the Worm's stupidity is its undoing, as the fact that it will mindlessly consume anything set in front of it allows one character to Feed It a Bomb. And after all, explosives blow up whether their target understands them or not.
- In Mercedes Lackey's Tales of the Five Hundred Kingdoms, the Tradition is the magical force that causes tropes to be continually reenacted, oblivious to the harm that does at the mortal level.
- The C'tan from Warhammer 40,000 used to be like this, being incomprehensibly ancient gas-clouds whose entire existence revolved around eating radiation emitted from stars. They weren't even aware of the existence of other life. Then the Necrontyr discovered them and gave them new bodies of living metal. The C'tan gained greater intelligence and awareness of the universe around them. Unfortunately, since they were still at heart creatures driven by the desire to consume, this only meant they now realized they could try eating things other than radiation — like lifeforce and souls.
- The Chaos Gods, Depending on the Writer both In-Universe and out, also may be like this. Some depictions have them as very clever, sapient and in full control of "the game of chaos" they are reputed to play (in other words, toying with mortals for their own amusement), while other depictions have them as single-minded entities doing only what they are made out of - anger for Khorne, desire for Slaanesh, change for Tzeentch and stagnation for Nurgle.
- Dungeons & Dragons:
- Banghtu, the orcish god of strength. While his physical might is almost limitless, he's known for being woefully stupid, one source giving him an Intelligence Score of only 3. (Making him dumber than most mortal children, orc or otherwise.) He values strength, and little else. The biggest benefit, however, is that his stupidity makes him completely loyal to his father Gruumsh, the head of the orc pantheon.
- Juiblex, the Faceless One: one of the most powerful demons ever, its mental attributes vary depending on sources with most of them giving it decent or superhuman levels of intellect, yet it still has the pathetically simplistic mindset of a slime, only thinking about engulfing, devouring and destroying everything on its way, to the point that other demon lords loathe it immensly.
- Pathfinder: While liches do become Stronger with Age, apathy tends to take over their minds as the years come by. They do less, and lose themselves in the process until their minds "decay", so to speak, due to sheer unrelenting apathy. Demiliches are the oldest of these, whose whole bodies aside from the skull have decayed from this process. They're possibly the most dangerous things an adventurer could ever face, able to rip your soul out with very little effort and carrying ludicrous magical might, but they're barely able to rouse enough thought to defend their possessions if touched, not even aware there's anything going on in their lairs otherwise.
- Call of Cthulhu features Azathoth, the ur-example. In the classic BRP, he has an INT of 0 and is literally mindless; in the d20 edition, he instead has Intelligence 3, the minimum intelligence for a sentient being. Trail of Cthulhu lacks stats for gods beyond the damage they do to Stability and Sanity, but they offer some alternate interpretations of Azathoth. One possibility is that it's a supermassive black hole that developed a rudimentary sentience; another, that it's a mathematical anomaly whose existence is pure agony and which seeks to destroy the universe that forces it to exist.
- Trope Namer Giygas is described as this at the end of EarthBound. He achieved ultimate power, but went insane in the process, and what Ness and company ultimately confront is a babbling abomination in a constant state of self-inflicted Mind Rape.
- The final boss of Silent Hill 3, as in the first game, is the God of the town's Apocalypse Cult, born incomplete, vicious, and feral after the priestess Claudia ingests it as a fetus. It is possible that the God appeared this way because Claudia is not the intended vessel, unlike the protagonist Heather, who carried the God in her womb throughout the game.
- John DeFoe of the Chzo Mythos was formerly an abused child who became a vengeful, murderous revenant after Chzo infused him with power after his father beat him to death with a possessed wooden idol. He's nigh unkillable, completely mad, and can do nothing but lash out at everything he sees. The tie-in short story The Expedition has one character express this opinion about Chzo itself:
"The King is a beast. That's the most foolish part of it. He has no sentience. His mind is nothing more than that of a fattened pig. He could be the most powerful entity in any universe and his actions are no more calculated than a dog chasing a bone."
- Deathevan, the Big Bad of Breath of Fire II, is strongly implied to be this. He's been propped up as the godhead of the Church of Eva for so long that he believes his own propaganda, appearing before the party as an old man in white robes before giving Ryu reason to attack him in a berserk rage. Once he's wounded, Deathevan's facade falls away, and his monstrous final form is a screaming lunatic that can't even comprehend why Ryu and his friends would fight so vehemently against him.
- The Legend of Zelda:
- In The Legend of Zelda: Oracle Games, Ganon becomes this due to a resurrection ritual that Link interrupts. Twinrova wanted to sacrifice Zelda, but when Link defeats her she sacrifices herself instead, bringing back all of the guy's power but none of his mind.
- According to Hyrule Historia, Ganon never fully recovered from his botched resurrection in the Oracle games; his next appearance in The Legend of Zelda being described as a beast deprived of Ganondorf's genius intellect, explaining why the final battle of that game is more of a simple King Koopa Copy boss fight in relative comparison to other games.
- In The Legend of Zelda: Breath of the Wild, even more so. Ganon is now a near-mindless monster incapable of speech who is only hate and malice incarnate. It's why he's known as "the Calamity Ganon" in this game: he's not a person or even a being, he's a destructive phenomenon, like an earthquake or a hurricane. Some characters, like the Old Man, go so far as to refer to Ganon as "it" rather than "him," due to Ganon's mindless nature.
- Yu Yevon in Final Fantasy X is little more than a computer program, running on a policy of:
10 PRESERVE Dream Zanarkand
20 SUMMON Sin
30 DESTROY Stuff
40 GOTO 10
- The Big Bad of Fire Emblem: The Blazing Blade, Nergal, gave into darkness to save his wife from some kidnappers. By the time he gets back, he's forgotten about her and is trying to corrupt his children into opening Dragon's Gate and starting the End of the World as We Know It. Badass Bookworm Canas also studies Dark Magic, and mentions that he must be careful, lest it consume him like his 3 brothers. If you find and complete the bonus chapters, Nergal mentions as he dies that he's forgotten something dear to him.
- In Mass Effect 2, Shepard boards a dead Reaper. The video logs from the researchers that previously investigated the ship bring this trope home:
Researcher: A god — a real god — is a verb. Not some old man with magic powers. It's a force. It warps reality just by being there. It doesn't have to want to. It doesn't have to think about it. It just does. ...The god's mind is gone but it still dreams.
- The Elder Scrolls
- In the series' primary Creation Myth, the God of Gods Anu and The Anti-God Padomay are the personifications of the forces of "stasis/order/light" and "change/chaos/darknesss", respectively. The interplay of these forces is what led to creation itself. From their "spilled blood" came the et'Ada, "original spirits", who would go on to become either the Aedra or the Daedra depending on their actions during the creation of Mundus, the mortal plane. Sithis, the "great void" embodiment of the force of chaos and said to be related to Padomay, is treated similarly.
- Lorkhan, also known by many other names, is the et'Ada who (depending on the storyteller) convinced/tricked some of the other et'Ada into sacrificing large portions of their divine power to create Mundus. For this perceived treachery, these et'Ada who made sacrifices (Aedra) punished Lorkhan by "killing" him, removing his divine center ("heart"), and casting it down into the world he helped to create where his spirit would be forced to wander. Most races of Mer (Elves) consider the creation of Mundus a malevolent act, which robbed their divine ancestors of their immortality and forced them to experience mortal suffering and loss. According to their religious teachings, Lorkhan is a powerful but "barely formed urge" of a being. Similarly, as Sep in Yokudan/Redguard tradition, he was created by Ruptga to help guide spirits to the Far Shores, but being driven by the same Horror Hunger that afflicts Satakalnote (having been formed from the "worldskins" that Satakal leaves behind), he attempts to consume those spirits and then, after being stopped by Ruptga, devises Mundus as an easier alternative to reaching the Far Shores. However, his plan is flawed and actually makes it harder for spirits to get there.
- In Dissidia Duodeceim, the aptly-named Feral Chaos is little more than a raging beast, the result of the game's main antagonist achieving even greater destructive power at the cost of his mind.
- In Sonic the Hedgehog (2006), Iblis is a godlike beast of phenomenal destructive power but no rational thought whose mindless rampage destroyed most of the world, ushering in a Bad Future. This is because he is the embodiment of the raw power of the sun god Solaris, while the conscious mind was split into another being, Mephiles the Dark.
- In Bloodborne, a line from Micolash suggests Rom the Vacuous Spider may be one of these. A theory that shows some credence since the word "vacuous" essentially means "mindless". In one ending, you may also become one when you ascend to become a newborn Great One.
- Haldos from Nexus Clash asserts that the true creator of the titular Nexus acts out of mindless instinct, and that the Powers That Be that players can align themselves with are lesser gods who came along much later. The latter is probably true, but Haldos is an Unreliable Narrator with an agenda to drive and it's unknown if he really knows the truth about the former.
- Omega in Final Fantasy XIV is an eons-old killing machine with one directive: to become stronger by facing down ever more powerful adversaries. Therefore, despite having the power to create entire worlds in his Interdimensional Rift, all of his efforts are spent organizing what amounts to a colossal tournament between the strongest beings in history and folklore in the hopes of producing a worthy opponent for himself. When confronted with a problem, his go-to option is lethal force: he nearly kills the Warrior of Light's allies on several occasions in an attempt to prod his "experiment" forward, and puts the Warrior of Light himself in a Death Trap purely to test a theory.
- Kirby Star Allies: Void Termina is described by the in-game flavor text as a being "born from the total absence of care" who has no sense of right or wrong. Sure enough, it spends the first quarter of its boss fight stomping around and smashing things with wild abandon. However, as the fight rages on, its attacks start getting a bit more strategic, and by the time Kirby and friends make it to Void Termina's core, it's "matured" into a living being capable of thought and emotion (but still corrupted by hate).
- In Stupid Snake, a textless webcomic, the title character is a stupid... snake with unlimited powers that randomly drive the plot that the poor main characters endure.
- One Saturday Morning Breakfast Cereal strip has the insane space monkey.
- Homestuck: It eventually turns out that Lord English is one of these. He used to be a Sburb player like the protagonists and had a ridiculously overpowered class (Lord of Time) that basically gave him total control over time and space. He's also a rather impatient person with questionable intelligence; he doesn't really understand the full implications of his time powers beyond using them as an instant Reset Button. Most of the time he just spams his other, more combat-oriented powers to win fights, not realizing that his time abilities would let him prevent the fights from even happening in the first place.
- In Orion's Arm, such beings are known as "Animin."
- Sauron, the Dark Lord of Middle Earth, is portrayed as senile in Plumbing the Death Star, having become so broken and delusional without his Ring of Power that even Saruman can't talk him into an actual strategy. Instead, the darkest force in Middle-Earth is reduced to simply screaming about throwing armies straight at his enemies.
- In Worm, Scion, the most powerful parahuman in the world and the first superhero, appears to be this. He doesn't appear to be able to prioritize, so he deals with flooded levies in Switzerland before dealing with the giant monster slaughtering superheroes and killing millions in New Delhi, and nobody can communicate with him to tell him about it. It's revealed that he's actually completely directionless with the exception of orders given by a homeless man in London, and the communication is infrequent enough that errors slip in. Many superheroes and villains refer to him as "the big golden idiot." Though is actually because he's a Sufficiently Advanced Alien and doesn't think the way a human would. Though he's still kind of an idiot, as he originally had a partner who did the planning, while Scion was the warrior of the pair.
- In the climax, Khepri fits this trope, having disabled the limitations on her power put in place to protect her mind. Over the course of the final parts of the story, her mind deteriorates even as she uses her boosted powers to save the world. By the end of the arc she's lost the ability to communicate with other people in any way, has lost nearly all her memories, and believes everyone is plotting against her - and very nearly becomes the setting's new Big Bad.
- SCP Foundation: SCP-3740, also known as "Ashur, God of the Windswept Plains and Soaring Skies". He genuinely is a god, and has enough control over the wind and weather to qualify as a Person of Mass Destruction. However, Ashur is also absurdly gullible even by mere human standards, and is convinced the researchers in charge of keeping him contained (basically by just telling him it's really important not to wreck the place he's in, please, and partying with him like the Assyrians of old) are actually fellow gods of his pantheon. As an example, he thinks the site director is actually an almighty cosmic all-father with power over the entire pantheon, and the only thing the director needed to do to demonstrate his godly might was flick a lightswitch off. Another genuine god shows up to pick him up only to decide to leave him to the Foundation and keep the deception going, as they're handling him admirably and entire Pantheons (plural; it's even said Jesus was the next in line to take care but he skipped town) are sick of babysitting the guy.
- My Little Pony: Friendship is Magic: King Sombra in his shadow form, while very huge, powerful, fluid, and able to spread with only a single fragment of his horn, is only capable of speaking small sentences and phrases and charging forward, in contrast to the highly-prepared sorcerer he once was. Though that could be because of the thousand years he spent trapped in ice.