->Self destruct lever. A mechanism that, for example, could flood your fort with magma, or release a trapped megabeast. For bonus points, build the whole fort on a single support.\\
'''Difficulty''': Very high. Extremely dangerous.\\
'''Usefulness''': None, by definition, but highly amusing.
--> -- '''VideoGame/DwarfFortress [[http://df.magmawiki.com/index.php/cv:Stupid_dwarf_trick Wiki]]'''

TheTimeOfMyths was a dangerous age to live in, with {{Eldritch Abomination}}s on the loose, [[GodOfEvil evil gods]] eating souls and whatnot. So it's not surprising that after becoming SufficientlyAdvanced, the {{Precursors}} made superweapons to defend themselves and make the galaxy or planet a safer place for their descendants. [[BenevolentPrecursors Conscientious precursors]] will dismantle or at least disable these weapons while [[FlingALightIntoTheFuture preserving them for later use]] -- usually by scattering the component {{Mac Guffin}}s across the cosmos or placing some kind of condition for activation (say VirginPower, or innocence).

Of course, most precursors tend to be either [[NeglectfulPrecursors neglectful]] or outright [[AbusivePrecursors abusive]]. What this means is that they will make these superweapons for no particular reason other than [[ForScience that they can]]. And even BenevolentPrecursors might have rogue elements or simply have their superweapons [[DangerousDeviceDisposalDebacle seemingly destroyed]] and thought lost amid the casualties but in fact thrown through time. The weapon itself may have had legitimate use once upon a time, but after making the planet destroying espresso machine to defeat Somnus the Snorer of Worlds, they will [[LostTechnology completely forget about ever having made it]] and leave it in an easily accessible location. The device will (of course) be [[RagnarokProofing immune to the ravages of time]] and ready to use minutes after being found. Worse, the precursors may not have even ''labeled the thing!'' So for all intents and purposes it seems like a normal espresso machine... which will destroy whatever planet it's on after one use. Of course, every villain or misguided soul in the setting will do whatever it takes to possess and activate the device, sometimes without even realizing (or underestimating) the danger it poses.

Alternatively, it represents something powerful with [[PotentialApplications great potential for abuse]] that is knowingly left behind. Lastly, it can also include examples of SealedEvilInACan where the evil could easily have been defeated, but wasn't for no good reason, forcing people to deal with an unrepentant and now further insane monster in the future.

It's as if the the US and Russia decided to "get rid" of all their nukes by putting rune encrusted marble doors outside every missile silo and left it at that. Oh, and the runes spell out "Come in, [[ThereWillBeCake there's punch and cake]]! Just turn both keys at the same time".

Not to be confused with the "plain" DoomsdayDevice.
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!!Examples:

[[foldercontrol]]

[[folder: Anime & Manga ]]

* In ''{{Slayers}}'', the elves created a powerful weapon that is immune to all magical attacks. It could also spit out smaller duplicates. Unfortunately [[spoiler: since the artifact is immune to all magic, it cannot be controlled. So, the elves just buried it and hope no one will ever find it.]]
* ''DragonBallGT'' brings us the black dragon balls. They appear to function exactly like those from DragonBall, collect all seven and summon an ancient dragon who will grant a single wish. Except that if they're used, ''the planet they were used on will be destroyed a year later.''

[[/folder]]

[[folder: Comic Books ]]
* [[GenericDoomsdayVillain Doomsday]] itself. He is created on prehistoric Krypton with the sole purpose to destroy all life with an absurd amount of brute strength to back it up.
* The [[MarvelUniverse Ultimate Nullifier]] is a device that can disintegrate anything (and sometimes more than that, depending on the continuity)--up to and including the entire universe. It's been used to stand off Galactus, but it's not at all clear why the thing exists in the first place, or why it's kept in Galactus' starbase.
** It's actually [[spoiler:a part of Galactus himself.]]

[[/folder]]

[[folder: Film ]]

* In the SoBadItsGood movie ''Film/PumaMan'', the artifact in question is a mask that can control minds. This mask was designed by a race of SufficientlyAdvancedAliens who believe that "Each man is a god, each man is free." This mask has no purpose other than to steal people's will, it can even be used to [[PsychicAssistedSuicide force people to commit suicide]].
-->'''[[Series/MysteryScienceTheater3000 Crow]]''': [[SchmuckBait Let's go drop it on some other planet, see who bites.]]
* ''Film/Plan9FromOuterSpace'': The aliens' motivation for (ineffectively) terrorising Earth is because they believe if humans continue to advance, we'll create exploding sunlight that will cascade-detonate the universe.
* The Russians' [[DoomsdayDevice Doomsday Machine]] from ''DrStrangelove'' actually had a very good point to it: to prevent nuclear holocaust by threatening to destroy the entire world in the event of a nuclear exchange -- the ultimate form of [[MutuallyAssuredDestruction mutually assured destruction]]. [[BlackComedy Unfortunately, the Russians hadn't gotten around to telling anybody about it just yet. They were saving the announcement for a special occasion, because, as the ambassador puts it, "The Premier loves surprises".]] As the eponymous [[MadScientist doctor]] points out, a deterrent isn't very deterring if nobody knows about it, which turns it into this trope.
* The Alpha-Omega Bomb from ''Film/BeneathThePlanetOfTheApes'', capable of [[EarthShatteringKaboom incinerating Earth's atmosphere]], was built only as a deterrent. Too bad a millennium later it would be [[CargoCult the god of a mutant group]]... [[spoiler:and actually be used!]]

[[/folder]]

[[folder: Stargate Verse ]]
In the ''Franchise/{{Stargate|Verse}}'' setting, the Ancients seemed to make a hobby of building these : most of the plots of ''Series/StargateAtlantis'' that aren't related to Wraith come from ridiculously dangerous unlabeled Ancient stuff. Downplayed, in that most of them had an actual purpose (killing Wraith), they just forgot to add, well, any failsafe or documentation. Prominent examples include:
* The Dakara Superweapon: capable of selectively disintegrating throughout the entire galaxy a particular species of life or all life in general, depending on how you set its incomprehensible but easily-used controls. Originally built to stop a plague and re-seed the galaxy with life.
* The Asuran Replicators: a form of machine life built as a weapon to destroy the Wraith but then abandoned to its own devices when it proved to be a "failure" in some undefined way. The Ancients at least did try to destroy it, but of course didn't do a particularly thorough job.
** Well, they actually did do a pretty thorough job, but since the [[GreyGoo Replicators]] are called that way [[MeaningfulName for a reason]], the few who survived rebuilt the civilization. So it's kind of like throwing an Ebola-virus sample away and [[TooDumbToLive assuming nothing wrong will happen]]. To their credit, the war with the Wraith is implied to have been quite advanced by that point, so maybe they just didn't have the resources available for a proper cleaning.
* Project Arcturus, an attempt to build a super-powerful power source that turned out to be highly unstable and that emitted unstoppable deadly radiation when in operation, plus exponentials amounts of energy (and, of course, the device can't be turned off once it starts to overcharge). Killed everyone on the planet with its radiation, but they left it in place for future tinkerers to mess with (and eventually wound up exploding, destroying 5/6 of the solar system it was in).
** After the original blew up, the Atlantis crew revisited the concept (and built it [[TooDumbToLive in their own city]]), and this time almost managed to destroy a parallel universe. Apparently they were fast learners.
* The device that gives anyone exposed to it exploding tumors.
* A weapon used for destroying Stargates. It can be used to maintain a wormhole indefinitely (Beyond the 38 minute limit), but doing so causes the gate on the other side to eventually overload and explode, taking most of the planet with it.
* Not to mention, you know, ''Atlantis.'' Which given the chair platform, super shields, and the Ancient database, probably qualifies as a whole squadron of doomsday devices, at the very least.
* A [[AGodIsYou God Game]]. Which worked by orbiting a few hundreds satellites over some inhabited planets, and a console to give the locals orders. Built by the same guys who, one ascended, forbid any interfering with lower planes because "[[AGodIAm Playing god]] in wrong".
** Noticeable in that Mc Kay and Sheppard had it mistaken for an Ancient VideoGame. Which means that either they built it without considering it any different from their ordinary video games, or their only one video game is about tricking real humans into thinking you're a god.
* A machine altering someone's DNA to make them ascend. Or die trying.
* It says something on the Ancient when the only non-ascended named one of the entire series, Janus, was kind of a MadScientist who built quite a few of these.
** Like a working TimeMachine. This one is an inversion, though : it's actually useful, doesn't have any nasty side effect we know about, and has a great potential for, you know, world saving and the like. Still, the Ancients were frightened of it and ordered Janus to destroy it (he didn't).
** The Attero Device, which was specifically tuned to Wraith hyperdrives to cause them to blow up during a jump throughout the galaxy. Unfortunately, it had the nasty side effect of causing every active stargate to explode in a [[EarthShatteringKaboom planet-busting]] manner. To his credit, the labo where Janus had left it was hidden fairly well, and he put a note on it which indicated "Has nasty side effects", making the Attero Device the best documented Ancient device ever.
* The worst thing about it is that, due to the aforementioned time machine, the Ancients were warned that Earth humans would one day visit Atlantis and the Pegasus Galaxy. They prepared accordingly, by programming a failsafe on Atlantis "submarine mode" (it resurfaces when the batteries that power it's shield are empty), an hologram about the Wraith controlling the galaxy, and [[ArsonMurderAndJaywalking lights that turn on when you arrive]], which was nice of them. It would have been nicer to, say take a few hours a destroy or at least document their explosive-tumors giving machines, leave a side-note about the Replicators, and a list of planets ''not'' to go to (because, you know, the Wraith control them) before they were ready. But, since most of the series' plots [[IdiotPlot wouldn't have happened then]]...
[[/folder]]

[[folder: Live Action TV ]]

* ''Series/BuffyTheVampireSlayer'' has multiple doomsday devices, spells and other various things.
* The planet-eating "doomsday machine" that appears in an episode of ''Series/StarTrekTheOriginalSeries'' seems to be one of these. Kirk can only guess as to where it may have come from or why it was activated, but he still has to stop it before it destroys anything else.
** His guess is that it was built for an ancient war that neither side survived after it was activated. If true the trope wouldn't apply, since it wasn't forgotten so much as it just kind of wandered off while still in use.
*** PeterDavid's [[Series/StarTrekTheNextGeneration TNG]] novel ''Vendetta'' expands on the doomsday machine: It was built as a last-ditch weapon by a race which had been nearly wiped out by The Borg. The one that Kirk destroyed was on an automated course, not to Earth, but ''through'' Earth to get to Borg territory. The one Kirk destroyed was also just the prototype. A far more powerful one has to be dealt with over the course of the novel. [[spoiler: Ultimately very very pointless as it attempts to go to warp 10 and gets stuck in the Dichotomy motion Paradox. Amazingly, references to transwarp (Voyager) don't really break continuity as you need special gizmos go into transwarp. The ship was just using a regular warp drive.]]

[[/folder]]

[[folder: Literature ]]

* Larry Niven's ''KnownSpace'' novels and short stories have one of these in the distant background, a device which supposedly ended the "Slaver Wars" and left fragmentary populations of survivors to survive into the distant future.
* The Franchise/StarWarsExpandedUniverse features the [[MarvelStarWars Shawken Device]], which is supposed to destroy the universe. It is notable for operating on principles that are considered dubious at best even by characters in the comic book in which it appears. But nobody really wants to test it, just in case. Luke and his sort-of apprentice even go to great lengths to disable it.
* Also from the ''StarWars EU'' is Centerpoint Station, a massive space station with the power to both move and destroy celestial bodies. Built by a ancient race called the Celestials, it doesn't seem to serve a purpose besides being a handy superweapon for the plot. [[spoiler:Until FateOfTheJedi revealed it SealedEvilInACan... Or rather, it was effectively a gun pointed at the Can that was supposed to go off should the Sealed Evil escape. [[NiceJobBreakingItHero Too bad the heroes blew it up in the previous story arc]].]]
* The Hypernova Bomb created by Hactar, and "given" to the Elders of Krikkit, in ''Literature/LifeTheUniverseAndEverything''. Hactar was original designed and built by the [[NamesToRunAwayFromReallyFast Silastic Armorfiends of Striterax]] and tasked with creating them an ''Ultimate Weapon''. On asking what they meant, it was instructed to "read a bloody dictionary". Whilst indeed pointless (it would blow up the entire Universe, leaving no victors but indeed making it the last weapon ever) it was a nice example of how the customer may be stupid but they are never wrong.
* In the third ''Literature/EmpireFromTheAshes'' book, the Fourth Empire's plans for an extremely-advanced gravitronic bomb capable of destroying a ''sun''--all on its own--are discovered. By this time, [[spoiler:the Fifth Empire is already well on its way to restoring its military might to the Achuultani-raping levels of the Fourth (with centuries to spare)]], so there's really nothing else to do with the plans besides let them fall into the hands of a highly-organized, widespread group of religious terrorists bent on toppling the government for allying with the ''minions of the AntiChrist!''
** The "bio-weapon" of the Fourth Empire probably qualifies for when it was invented, as well. No amount of paranoia over the yet-unseen wave of genocidal invaders can make other than mindbogglingly ''insane'' the creation of [[spoiler:[[ThePlague a rapidly-evolving super plague]] that destroys ''all life'', has a very long dormancy period, and cannot be cured. That it turns out they could have effortlessly wiped out the invaders with their current military power just makes things worse]].
* ''Possibly'' the Time Matrix from ''Literature/{{Animorphs}}.'' In ''The Andalite Chronicles,'' it was implied to have been created by [[SufficientlyAdvancedAliens the Ellimist(s)]], the theory being that he/they used it to AscendToAHigherPlaneOfExistence in the first place. Years and dozens of books later ''The Ellimist Chronicles'' told the ''real'' story of how this happened, and the Time Matrix didn't even get a mention. So, who knows?
** There is a bit of [[JustifiedTrope justification]] for it just being left behind, though--neither the Ellimist nor [[EldritchAbomination Crayak]] want the other's side to have it, so their "game" presumably has a rule about neither messing with it (until they had to in ''Elfangor's Secret''). Still leaves its origin (and [[NoodleIncident how it got on Earth]] before the [[TheGreys Skrit Na]] found it) a mystery.
* TheMagiciansNephew has the Deplorable Word which, once spoken, will eliminate all life in the universe other than the speaker. Its pointlessness is sort of the point.

[[/folder]]

[[folder: Tabletop Games ]]

* One of these [[LostTechnology left behind]] by the [[AndManGrewProud Blackmoor civilization]], then found and [[IdiotBall tinkered with]] by some ignorant elves, is the reason why one region of the {{Mystara}} game-setting is known as [[{{Mordor}} the Broken Lands]].
* Played with in ''{{Warhammer 40000}}''. Finding ancient doomsday weapons with no clear purpose evident is pretty common, but the setting being what it is, pretty much all of them did have a purpose at one point in time. The Blackstone Fortresses, for example, seemed pointless until the Necrons, whom the Fortresses were built to combat, returned.
* Many First Age superweapons in the ''TabletopGames/{{Exalted}}'' setting fall in that category. After all, we are speaking of a GoldenAge where the war against evil was supposedly ''won'', so why the hell did the Exalted continue to manufacture and stockpile world-theatening weapons in such extents? Sure, the defeated enemies (Yozis, Neverborns and Rashka) are still around and that totally justifies some things. The Realm Defense Grid, for example, is a rather well designed superwapon, which has world-shattering capabilities but can also be used for more small-scale and limited warfare, and comes with serious security systems and safety mechanisms. But honestly, what good can come from things like [[FantasticNuke Thousand-Forged Dragons]], [[NeutronBomb Soulbreaker Orbs]], or mass destruction Solar circle spells such as Rain of Doom? They are clearly more suited to devastating Creation and killing a massive number of people than to waging an efficient war against demons, undead or fairies.
** The only people responsible enough to make something about that after the Primordial War are the Maidens of Destiny, who sealed away the most powerful weapons of their servants (the Greater Signs and the Astrological Charms, which basically allow you to directly rewrite the fabric of the universe) and hope they will never need to be used again (although Saturn is probably no fool about this -- after all, there is always an ending...)
* ''TabletopGame/ForgottenRealms'' -- The [[HatePlague Dracorage]] Mythal, a device designed to put ''every dragon in the world'' at once into [[AxCrazy murderous madness]]. As an added bonus, the damn thing actives automatically every time a specific comet passes overhead. It had a logical purpose at the time of its construction and initial activation, but by the time it had thoroughly served that purpose (smashing draconic civilization beyond all hope of reconstruction) no-one alive knew how the Dracorage Mythal worked, or where the control system that could be used to shut it down was.
[[/folder]]

[[folder: Video Games ]]

* In ''VideoGame/DwarfFortress'', making these is a [[ComedicSociopathy typical dwarven hobby.]] They usually involve [[LavaAddsAwesome magma]]. Notable examples from [[LetsPlay succession games]] include {{Boatmurdered}}'s Project: Fuck The World (which incidentally shortens to FTW), and Headshoots' [[spoiler:WEAPON.]]
** Boatmurdered's FTW is more an example of a standard DoomsdayDevice, in that it was used repeatedly and to great effect protecting the fortress from ''everything'' from [[OurGoblinsAreDifferent goblin invasions]] to [[{{Golem}} Bronze Colossi]] to unfortunate merchant caravans who arrived at just the wrong time. [[spoiler: The fact that it ultimately lead to the firey downfall of the settlement is more a tribute to its epic mismanagement.]]
** Best of all, succession games incorporate the "LostTechnology" aspect of the trope -- within real-time days or weeks, as one player constructs such a device and connects levers to it, but then doesn't label any of the levers so that a few players later, somebody inherits it and literally has a) no idea how to activate the device if they wanted to and b) no idea which lever does what. The results are pretty much inevitable, especially given that tantruming dwarves often throw levers without being ordered to.
*** Boatmurdered also featured a lever to flood the siege workshop. None of the players could remember why (the room had formerly contained a farm plot).
** Headshoots had one hilarious example; a failsafe switch for [[spoiler: WEAPON]] is right next to and the same colour as a device that releases all the cats from a cage.
*** So saving the world involves killing your framerate?
*** Who said anything about "saving?"
** In Syrupleaf, the same lever somehow got connected to both the outer drawbridges and the irrigation floodgates, so [[http://lparchive.org/LetsPlay/Syrupleaf/Update%2046/index.html raising the bridge to protect the trade depot would flood the farm plots]].
** It used to be (It still is to a lesser degree) that anything caught under a closing drawbridge would be utterly destroyed, removed from the game. This was refered to as the Dwarven Atom Smasher, and was useful for everything from destroying enemy seiges to [[MundaneUtility getting rid of garbage.]]
** Check out the community pages (The forums and the wiki) for plenty more examples. Most notably, the wiki offers a suggestion that players build a 'doomsday clock'; a mechanism that will, if a certain pressure plate is not triggered for X amount of time or some other condition is not met, destroy the fortress and render it permanently uninhabitable.
** The succession game famous as Boatmurdered 2010 Battlefailed had FAILCANNON similar to FTW but was designed so that the faucet was a giant skull. It lived up to its name [[spoiler: at first, after reclaiming the fortress they rebuilt FAILCANNON and are currently [[http://www.bay12forums.com/smf/index.php?topic=76193.60 testing it as we type this]]]]
* Just whom did the {{Precursors}} of ''StarControl'' have to deal with that warranted the fleet buster that was the Sa-Matra? And why would they leave it behind when they left the Galaxy?
** Well, we know the planet-busting bombs that was used to destroy it were engineering tools ...
** And it is arguable whether they left the Galaxy at all. The device may have been intended for use to fix "mistakes" (like [[spoiler: the Mycon and Daktaklakpak]]).
* The ''Franchise/{{Ultima}}'' series has the Armageddon spell, which will wipe out all life in the universe. (except Lord British, and sometimes the caster is immune too. Sometimes.) In ''VideoGame/UltimaVI'', you're given the spell as a freebie by the Xorinite, hoping to entice you into taking advantage of their information-brokering services. They don't think the spell is very impressive since it only affects the current plane of existence.
* Played with in ''VideoGame/TalesOfSymphonia'' and ''VideoGame/TalesOfPhantasia''. The superweapon, the Mana Cannon, wasn't left behind- the plans were. Despite the weapon ultimately being the destruction of ''every society to use those plans'', its one of the first things to be built when magitechnology rebuilds from the inevitable knocked-back-to-the-stone-age that always follows its construction. Except in Symphonia, where it didn't destroy the world — but proved mostly useless in saving it too.
** Admittedly, one time it was used, [[spoiler: there was a meteor strike ''immediately after.'' It is a little unclear about whether the Mana Cannon itself destroys civilization or if the users just have ''really bad timing.'']]
* This was Dr. Ivo "Eggman" Robotnik's M.O. from about 1998-2008 in Franchise/SonicTheHedgehog. He would look for some SealedEvilInACan, often a god or EldritchAbomination of some sort. It would almost always run amok until [[BigDamnHeroes Sonic and his pals]] invariably showed up. [[VideoGame/SonicColors Lately]], [[VideoGame/SonicTheHedgehog4 how]][[VideoGame/SonicGenerations ever]], he seems to be creating original plans again.
* In ''VideoGame/{{Fallout|1}}'', The Cathedral's basement has a fully functional atom bomb that can only be used to destroy the Cathedral. Just in case The Master decides his Master Plan is flawed beyond salvation and just wants to end it all instead of finding a new plan, or telling the people working for him. Also very convenient if some aspiring person with technical knowhow happens to disagree with the Master Plan and makes an unannounced visit.
** It was also a secret contingency in case the Unity met a enemy it could not defeat, they would destroy them with it. Still kinda baddly guarded for a doomsday weapon, through.
* The Thermonuclear Detonation spell of the ''VideoGame/QuestForGlory'' series. [[ExactlyWhatItSaysOnTheTin It causes an explosion with the strength of a nuclear warhead to occur]] -- centered on the hero. This causes an automatic game over, since it kills you and destroys the nation you are trying to save at the time.
** It could conceivably be useful to know if the player character had a proper grounding in magical theory and could research or reverse-engineer spells. The spell might have been inscribed as a succinct example of basic principles rather than a weapon for an adventurer's arsenal.
* ''VideoGame/FinalFantasyX2'' has [[spoiler:Vegnagun. It is a powerful superweapon, yes, and would probably be actually quite useful -- if it didn't destroy the ''entire world'' upon firing.]]
** If fired up at the roof of an underground cavern, then yes it will blow the surface above to smithereens. Presumably that is not how it was meant to be used. The reason it's sealed away is because it has a broken IFF.

[[/folder]]

[[folder: Web Animation ]]

* ''WebAnimation/TheDementedCartoonMovie'' has [[DoomyDoomsOfDoom "The Evil Machine Thing O' Doom".]] {{Lampshaded}} when [[BigBad Evil Blah]] asks "Alright, what the hell does that machine do?" As it turns out, it does nothing but shoot goo out.

[[/folder]]

[[folder: Web Comics ]]

* The [[DinosaursAreDragons dragons']] iridium bomb in ''TheInexplicableAdventuresOfBob.''

[[/folder]]

[[folder: Western Animation ]]
* In ''WesternAnimation/{{Futurama}}'', Professor Farnsworth's hobby is basically making spare {{doomsday device}}s in the same way old women knit sweaters.
** He even has a sentimental favorite. The Sphere-O-Boom.
** He now has a cabinet labeled ''Surplus Doomsday Devices'' which is full of more doomsday devices, including ''another'' Sphere-O-Boom.
--> '''Professor Farnsworth:''' I suppose I could part with ''one'' and still be feared...

[[/folder]]
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