History Main / DangerousForbiddenTechnique

** This is the effect of pushing the engine past its rated limits. What's on paper is what the manufacturer has safely determined the engine will go up to without dying sooner than how long it's expected to last. You could always push an engine harder, but doing so wears it out faster.

* The entire point of TheDarkSide in StarWars.

* In ''Literature/TheMagiciansNephew'', the {{Prequel}} to Literature/TheLionTheWitchAndTheWardrobe, there is a dark spell the Deplorable Word. When it is spoken, every form of life in the world with the sole exception of the speaker is killed instantly. [[BigBad Jadis]] actually boasts about the extensive measures she took to learn this and then use it to kill everybody in her homeworld as part of her backstory. [[WorldWarII Considering the time Lewis wrote it,]] [[SomeAnvilsNeedToBeDropped it's quite blatant]] [[AtomicHate what it's supposed to symbolize.]]

* Backfired with the destruction of HMS ''Invincible'' at Jutland. The DangerousForbiddenTechnique in this case was the bypassing of safety protocols designed to prevent flashdown of a detonation in a turret from reaching the magazines, and it was done to increase rate of fire. But ''Invincible'' was pounding the crap out of the German SMS ''Lutzow'', so why not? Why not, indeed. The mist that was hiding her cleared, just long enough for the critically damaged but afloat ''Lutzow''[[note]]At the end of the battle, ''Lutzow'' was too badly damaged to withdraw and was scuttled.[[/note]], along with a second German battlecruiser SMS ''Derfflinger'', to get some solid hits in in the right place, and ''Invincible'' was blown in two. At least one and possibly both of the other British battlecruisers lost that day went up for the same reason. The fact that British ships of WorldWarI used a more volatile gunpowder than their German counterparts didn't help, either.

* The bonehead maneuver in ''Series/BabylonFive'': Opening a jump gate within an existing jump gate, resulting in a massive explosion of energy that the ship who triggered it is highly unlikely to survive or outrun. The heroes only use it because it was the only way they could think of to shake the Shadow ship trying to kill them.

* Death magic in LoisMcMasterBujold's ''Literature/{{Chalion}}'' series causes both the target and the caster to die as their souls are borne off to the Bastard's Hell (when it works at all). Luckily for some so affected, not only is the Bastard's Hell is not only more of AHellOfATime than a FireAndBrimstoneHell, but they don't always stay there, as some of the other gods may take them up. Not to mention that unsuccessful attempts/research are regarded as attempted murder at best and dealt with by temporal authorities as such.

* The use of "balefire" in Robert Jordan's ''Literature/TheWheelOfTime'' is forbidden by the magic users of the world, and when people use it anyway, they're exceedingly careful with it - because balefire doesn't just obliterate its target, it goes ''back in time'' to do so, with all the potential paradox that implies. Entire cities and their recent histories disappeared from the face of the earth before the mages, good ''and'' evil, decided that maybe gratuitous use of balefire wasn't such a good idea... When Rand begins using it for more than minute uses it is seen as a sign of his rapidly deteriorating mental state impacting his judgement, though he is technically correct that balefire is the only way to ensure enemies such as the Forsaken are not ressurected by the Dark One.

* A ''WesternAnimation/BatmanTheAnimatedSeries'' episode has a ninja steal a scroll in Japan that teaches him the secret of a "deadly touch" technique. When Batan faces him off in the end, he tries to avoid being touched by the guy in a specific spot, which (theoretically) would cause instant death. He fails and falls down, seemingly dead. He then gets up and knocks out the bad guy. When asked if the technique was bullshit, he pulls out a [[PocketProtector metal plate]] from under his suit, which has been deformed by a strong force.

* In ''KissOfTheDragon'', JetLi describes the titular technique as "very secret, very forbidden". (Though that technique actually poses no danger to the user. It is forbidden because of its effect on the target.)
* In ''BladesOfGlory'', the Iron Lotus is a technique developed by the coach in his "wild youth", but only one country was crazy enough to try it - North Korea. The only attempt resulted in the woman's head cut off by the man's ice skate (as impossible as this sounds). According to the coach, the only way for the technique to be performed successfully is by a pair of two men.

* The destruction of HMS ''Invincible'' at Jutland. The DangerousForbiddenTechnique in this case was the bypassing of safety protocols designed to prevent flashdown of a detonation in a turret from reaching the magazines, and it was done to increase rate of fire. But ''Invincible'' was pounding the crap out of the German SMS ''Lutzow'', so why not? Why not, indeed. The mist that was hiding her cleared, just long enough for the critically damaged but afloat ''Lutzow''[[note]]At the end of the battle, ''Lutzow'' was too badly damaged to withdraw and was scuttled.[[/note]], along with a second German battlecruiser SMS ''Derfflinger'', to get some solid hits in in the right place, and ''Invincible'' was blown in two. At least one and possibly both of the other British battlecruisers lost that day went up for the same reason. The fact that British ships of WorldWarI used a more volatile gunpowder than their German counterparts didn't help, either.

* ''VideoGame/OdinSphere'' has Oswald's shadow form. In gameplay terms it vastly increases his attack speed and power, at the cost of rapidly eating away as his POW meter (which, if depleted, causes him to become exhausted and unable to move or attack until it refills completely.) In story terms, using it too much will destroy Oswald's soul and turn him into one of the ghostly Revenants haunting Winterhorn Ridge [[spoiler: which eventually does happen in one of the bad ending scenarios, is Oswald is pitted against Onyx.]]
** There's also the Darkova spell, which transforms the user into a massive, powerful cerberus. The former king of Titania used it once to try and fend off enemy forces and went mad with power, ravaging Titania for seven days until he was finally slain by his son. [[spoiler: Ingway finds out how to use it, and it similarly comes back to bite him as soon as he does.]]

* In ''TabletopGame/{{Ironclaw}}'' [[BlackMagic Unholy magic]]/{{Necromancy}} summons vengeful spirits to do magic for you, there is a chance that these spirits will do other things like animate random corpses, possess people (including the caster), or make scary sounds that freak people out.

* The title character from {{Inuyasha}} can allow his demonic blood to temporarily dominate him by casting aside his mystical {{BFS}}, or having it stolen, which means it borders between this trope and SuperpoweredEvilSide. This "demon form" makes him a lot stronger but the more times he uses it, the more [[DeadlyUpgrade his soul decays]]. This may not sound like much, but what it actually means is that he becomes a [[UnstoppableRage berserk, vicious killer]], and the more time he spends in this form, the more indiscriminate he becomes in choice of targets. It also becomes easier and easier to activate, and harder and harder to turn off... which means that he will, ultimately, become nothing but a mindless killing machine that can do nothing but wander aimlessly and slaughter everything in sight.
* ''RurouniKenshin'' used this trope on both Shishio and Kenshin. [[spoiler: The full body-bandaged Shishio would and did die from heat exhaustion after 15 minutes. Kenshin was forced to retire from swordmanship for good because of his overuse of the Hiten Mitsurugi Ryuu, as his fighting style is meant for more muscular men.]]

* In ''Manga/OnePiece'', during the Skypiea arc, there happens to be a device called a Reject Dial, which is ten times stronger than the much more common Impact Dial. Using this has a large chance of destroying the user as well as his or her opponent. Wiper, A character intent on killing the Big Bad of that arc with the Reject Dial, uses the item ''thrice'', and though his body does take massive damage, he escapes alive.

** In general, ''any'' ability gained by Devil's Fruit may be considered this. Some abilities can give the user amazing powers (some are more useful than others) but it always comes with a potentially lethal side-effect: The user loses the ability to swim, permanently. Pirates who take a chance and use the stuff are truly risking their lives, especially those who brave the dangers of the Grand Line.

* ''{{Castlevania}}: Order of Ecclesia'',has the Dominus glyphs, Dominus Anger and Dominus Hatred are direct attack glyphs with each use inflicting shitloads of damage at cost to your HP, and Dominus Agony amps all your stats immensely with gradual HP loss thrown in on top of that. Unless you use a healing item at some point, prolonged uses of these glyphs by themselves will kill you. The Dominus glyph union kills everything in the area - Shanoa included [[spoiler: unless you're using it at the end of the last battle, where Albus's soul takes your place for the sacrifice.]]

** Something else mentioned in the ''Book of Vile Darkness'' is the ArtifactOfDoom called the [[NamesToRunAwayFromReallyFast Death Rock]]. Artifacts are always dangerous, but this one is worse than most; it's history does say that its owners tend to obtain great power and are able to conquer empires, but tend to lose the power at the worst possible time, and are usually overthrown in violent insurrections by their enemies. Here's how the Rock works: It gives the user incredible dark powers of [[{{Necromancer}} necromancy]], giving him the potential to raise vast undead armies. But it has a terrible cost; once a week, it demands the user slay his closest friend or loved one, and claim him or her as a zombie slave. If he is unwilling or unable to do so, the Rock and all powers associated with it vanish. Clearly, all former users never realize that if you are willing to do this, you're going to run out of friends and loved ones ''very'' quickly (a lot of them will likely stop being your friends before you can use them as the required sacrifices) and be unable to make ant new ones; on the other hand, you'll probably make hated enemies ''very'' fast...

* The first four [[DotHack .hack//]] games feature Data Drain, a technique that allows the user to either severely weaken a computer-controlled enemy, or MindRape a human being (most humans hit with a Data Drain end up in comas). The hero, Kite, is the only human with the ability. He uses it to weaken game enemies that have been hacked so as to have infinite HP, thereby making them defeatable, and to gather virus data to hack into protected areas of the game. The catch is that repeated use will corrupt his character data with the virus, causing nasty side effects in battle and, eventually, his character's death.

* In ''Fanfic/{{Pokeumans}}'', [[SpiritAdvisor Spiritus]] reveals to Brandon that as an Energy Channeller he may be able to perform Total Absorption - which would consume the enemy's aura (and by default, [[ThouShaltNotKill is totally fatal]]) and may even take a hit on his sanity to the point of unleashing a SuperpoweredEvilSide.

If the hero is ''lucky'', it could just be a HeroicRROD. But it's often worse than that.

* In ''TabletopGame/DungeonsAndDragons'', there exist two magic staffs, the ''staff of power'' and the artefact ''staff of the magi'' which, while very powerful items in themselves, can be broken for a "retributive strike" which releases every spell inside the staff at once, centred on the caster. Given that the SquishyWizard is the norm in D, anyone attempting this strategy had better hope that the 50% chance of getting sent to another dimension comes up.

** This is the point of the corrupt spells in the Book of Vile Darkness (and their Exalted Deeds counterparts, sacrifice spells). They are notably more powerful than other spells of their level--for instance, run-of-the-mill Blindness is a second-level spell, while Seething Eyebane, a corrupt first-level spell, causes the target's eyes to spew acid and explode--but there is always a tax, sometimes permanent, on one or more ability scores. The most powerful of these spells is harmful even to prepare and has a very good chance of rendering the caster dead and/or permanently insane [[OmnicidalManiac (if he wasn't already)]].

** A wizard's death curse. Put simply, the wizard, usually when knowing she is about to die, draws up all the power stored in her body and mind and unleashes it in a powerful spell, usually a curse on whoever was killing her. Of course, this leaves no energy to keep the brain or heart working, so the wizard dies immediately on casting.

* Ryoga Hibiki's "Shishi Hōkōdan" in ''RanmaOneHalf''. This [[KiAttacks Ki Attack]] is fueled by the user's depression and melancholy. So to acquire more power the user will purposely do things to become more depressed. When Cologne sees Ranma and Ryoga trying to out-depress each other while blasting the technique freely, she compares them to a pair of lions fighting as they roll off a precipice and to their deaths.

** The Shishi Hōkōdan is actually an interesting example on two accounts. First, Ranma tries and fails to beat Ryoga at his own game, and realizes the flaw in the principle-namely, as the tide of battle turns, the loser will gain great power for the technique by his depression at losing the fight while the winner's lightened spirits will depower the technique. So he creates his own, Not-So-Dangerous, Not-Actually-Forbidden Technique in the form of a KiAttack fueled by boundless confidence. Second, Ryoga is baffled when the scroll he learns the technique from indicates a general sense of downwardness; it turns out that in it's purest form Shishi Hōkōdan isn't a directed beam, it's more like a weight dropping on the user from the heavens; the user is protected from his own attack because he's emotionally empty when he uses it. Ranma uses this against Ryoga by jolting him out of his reverie mid-attack with [[PantyShot something he knows Ryoga wants from Akane]]; the surging hope and anticipation leave Ryoga open to being clobbered by his own technique.

* In ''TheMagiciansNephew'', the {{Prequel}} to TheLionTheWitchAndTheWardrobe, there is a dark spell the Deplorable Word. When it is spoken, every form of life in the world with the sole exception of the speaker is killed instantly. [[BigBad Jadis]] actually boasts about the extensive measures she took to learn this and then use it to kill everybody in her homeworld as part of her backstory. [[WorldWarII Considering the time Lewis wrote it,]] [[SomeAnvilsNeedToBeDropped it's quite blatant]] [[AtomicHate what it's supposed to symbolize.]]

** Earlier in the series, ''Portrait of Ruin'' subverts the hell out of this. Pretty much for the entire first half of the game, you get warned about how having Johnathan or any other non-Belmont use the true power of the Vampire Killer will drain their life force and eventually kill them if they overuse it. But when you do actually unlock its power in game, [[DoubleEntendre you can whip it all day long with absolutely no consequences whatsoever.]]