Terminally Dependent Society

An entire ship, city, society, planet or galaxy that depends on a single piece of Phlebotinum to survive. This piece of phlebotinum can take any form: It may be a Master Computer that sees all and plans everyone's day, a Hive Queen or Fisher King keeping the subjects in a Lotus Eater Machine, a Genius Loci that maintains a Ghibli Hills Utopia, or a spiritual source of life. More mundane depictions might use it as the energy for Faster-Than-Light Travel or the entire planet. Or maybe it's just magically linked to every citizen, or to the land itself. In any case, no one can imagine living without it... or literally live without it. It may or may not be sentient, but the point is it's grown completely beyond the control of the people. Even in those cases where it's originally man-made.

Then it breaks down. Or disappears. Or becomes sentient and decides to Kill All Humans, play games with them, or worse, smother them with love. Or it absorbs all lifeforms into itself and becomes a God. And everyone who depended on it is now doomed. The technology that was used before the machine was invented has long since been forgotten, or the dying life source makes the citizens magically ill, or it's simply grown too strong and humanity has become too weak to fight back. This is especially common when the Phlebotinum is Powered by a Forsaken Child.

Being doomed isn't always a bad thing, though. Maybe the society simply Ascends to A Higher Plane of Existence, or discover The End of the World as We Know It means their world has simply changed, not ended. They can survive just fine by giving up the wanton hedonism of their old existence. Of course, it may turn into an Inferred Holocaust if no one knows how to plow a field. Or maybe the good guys can use the energy source to conquer all the bad guys who depend on it.

Fantasy and Scifi like to use the Terminally Dependent Society in conjunction with a Fantastic Aesop about the dangers in abusing Aesoptinum. This is often paired by having it created by foolishly enthusiastic scientist, you can expect its noxious properties to manifest quickly. Interestingly, a Mad Scientist who designs a dependence causing device in order to take over the world will have it break down/addict him/escape his control as punishment for his Pride.

In sci-fi, it's almost always a metaphor for the internet. In fantasy, it's generally a metaphor for limited fossil fuel. Generally, these aesops lead to No Blood for Phlebotinum. Expect two or three characters to escape and become the new Adam and Eve. Mind the inbreeding.

A lot of sci-fi stories predicted the internet, and many of them describe a society completely depending on it. One of the earliest is from 1909. There's probably earlier ones out there, but in any case this trope is Older Than Radio.

In horror stories, it can close every door, remove air supplies wherever it wants, create monsters or Hallucinations, and it probably looks like a humanoid Eldritch Abomination spouting existentialist Author Filibuster once the heroes finally destroy it.

See also: No Ontological Inertia, Bee People, Keystone Army, Cosmic Keystone, The Magic Goes Away. Creating this set up is a common means for an Evil Overlord to try and seize power. Or the creator/controlled uses it to seize power.

Films -- Animated

 * The humans in WALL-E depend on their ship for all sustenance. The fact that does not change the fact that  the humans cannot live anywhere except on board the Axiom.
 * In Atlantis: The Lost Empire, the Atlanteans and their city are dependent on . It gives them vitality and a ridiculously long lifespan through   which stop glowing when the power source is taken away, and Milo explicitly tells Rourke that they'll die if he doesn't return it. However, no one but the King seemed to know about the 's influence, though whether they all forgot with time or never knew to begin with wasn't revealed.

Films -- Live-Action

 * The glowy Eywa tree in Avatar stores memories and coordinates the global ecosystem, it was almost destroyed until the self defense function was triggered.
 * Similarly, the Unobtainium was vital to the humans. While not strictly crucial for survival, it was important for interstellar travel to mitigate the overcrowded, overindustrialized homeworld. The only use for Unobtainium shown in the film was to get to Pandora... to get more Unobtainium. No talk of colonization.
 * The City of Ember with its hydroelectric generator.
 * The vampires in Daybreakers are a society terminally dependent on blood. And they're just shy of wiping out humanity when the movie starts. Whoops.
 * The main computer in Logan's Run. After it learns that Sanctuary doesn't exist, it freaks out and destroys the city, forcing the inhabitants to flee.
 * The robots in The Matrix are able to take over, because they got too powerful for humans to control. The dependent relationship is explored in the animated short prequel film The Second Renaissance.
 * In Space Transformers (a Joseph Lai film) the fate of the universe depends on a woman named Ivy who has a galaxy inside her body.

Literature

 * In the end of The Pendragon Adventure's The Reality Bug,
 * E.M. Forster's The Machine Stops: humans in the future depend entirely on The Machine, and never leave their rooms anymore. Written in 1909.
 * In several of Isaac Asimov's stories, future humanity is fully controlled by Multivac/AC; however, "The Life and Times of Multivac" is the only one in which the dependent society becomes obliged to do without.
 * In another story of his, there's a subversion: An overwhelmingly large percentage of the population are incapable of doing simple math problems. When someone rediscovers how to do it by hand, a country uses it to get rid of computers in planes to make faster, lighter aircraft because they can perform the math by hand, giving them an edge on whatever country they're warring against.
 * Arthur C. Clarke's The City and the Stars. The Central Computer of Diaspar not only runs the city but actually creates its citizens' bodies using their stored memories. In a variation on this trope, the computer wants humans not to be dependent on it anymore, and has
 * The Machine in the John W. Campbell short story of the same name. It controlled the entire Earth, and as a result the human race had become dependent on it.
 * Mike the computer from Robert A. Heinlein's The Moon Is a Harsh Mistress is a benign example: he helps the heroes plan a revolution, using his surveillance system and his complete control over transport, visual media and government documents.
 * Lampshaded by the main character, a computer technician, who notes that hooking everything (including the whole life support system) up to one source makes a society really vulnerable.
 * From Harlan Ellison's I Have No Mouth, and I Must Scream: The internet/computer system AM ends up becoming a God and destroys humanity.
 * One of the early Mad comics (from before the magazine-style revamp) featured a story called "Blobs" which parodied this concept.
 * In Crowned Kreg series by Olga Larionova people of one planet after a catastrophe were blind from infancy and lived in symbiosis with other sentients who gave their vision via limited telepathy (and were rewarded quite well). When it turned out it's not that simple and utopic and not even close, the disagreement proved disastrous -- everyone's still blind without 'em.
 * The cities of the Khaiem from The Long Price Quartet are dependent on the Andat for defence and economic prosperity. The andat are abstract concepts made physical that grant total power over that concept e.g. Stone-Made-Soft, Clarity-Of-Vision, Water-Moving-Down etc. The Khaiem have no military power and relatively little technology. The over-dependence on the andat is a major theme of the series.
 * The entire world of Matrin in The Secret Texts originally ran on enormous magic usage. Things get extremely ugly and deadly when their source gets cut off.
 * Council Wars is a near Utopia, Mother controls the planet, there are a few A Is separate from her from long ago wars that fought on the winning side. Everything you could want is available. Everyone has a power allotment from Mother, although one can trade power as currency for various tasks either the A Is are unable to do or people prefer not to do (such as certain forms of medicine humans are better at). Most people just play various games or try changes to explore other forms of life. Some people choose to become Merpeople, others to fly. Some people upload to nanites. Something between World of Warcraft and LARP occupies many folks times. Various historians and folks with interest keep up random hobbies from horticulture to smithing. Some folks even change into dwarves and have fun mining. Then a political argument breaks out because humanity hasn't had any real advances in 500 years and birth rates are so low as to threaten the species. One side, believing humanity has become a Terminally Dependent Society, decides to overthrow the Status Quo. The 13 Council members then take all the power upholding the system and fight with it.
 * Dune's interstellar society is utterly dependent on the 'spice' that can be harvested only on planet Arrakis. One book even points out what would happen without the spice: hundreds of billions would die of withdrawal, interstellar navigation would be impossible, millenia old human breeding programs would collapse, etc.
 * In Stationery Voyagers: Without the Muellex, all life-supporting worlds would crash into each other suddenly due to their proximity. Also makes the Muellex something of a Cosmic Keystone, since only one world supported all derivatives of humanity originally, and the current setup is only because evil entered the world when Dabor ignored orders not to release the Muellex to begin with.
 * In the short story "The Ones Who Walk Away From Omelas" by Ursula K. Le Guin, the prosperity of the titular city is dependent on treating some poor kid like crap. If the child's suffering was ever alleviated, all of Omelas would suffer instead. Every citizen of Omelas is made aware of this terrible price. Most of them rationalize it away as something necessary for the greater good and live their lives to the fullest knowing the cost. And then there are those who decide it isn't worth it, and walk away from Omelas.
 * Scott Westerfeld's Uglies takes place in a future where our current society has been destroyed due to a plague that burns up all our oil. The future society thus tries to avoid this trope, making sure to carefully manage their use of natural resources, only to since, as David Lampshades, they were dependent on a mandatory operation that made everyone beautiful and
 * Derek Gunn's Vampire Apocalypse the Series has vampires relating to human beings this way. It's also a metaphor for humanity's relationship with oil, which resulted in the whole situation.
 * The Novels of the Change show that humanity in The Nineties (let alone our time) would undergo The End of the World as We Know It without trucking and tractors (other linchpins knocked out by said Change include electricity, explosives and steam power, but internal combustion is the most immediately lethal one).
 * Food might seem like a slightly obvious one to mention, but Ankh Morpork is apparently only a few meals from going hungry even at the best of times.
 * John Varley's Steel Beach: CC, the Central Computer that runs everything on Luna, goes insane.
 * The final pages of The Return Of The King reveal that wore one of the three elven Rings of Power, and  is revealed to have another in The Fellowship Of The Ring. It's strongly implied that these Rings were the only real protection for Rivendell and Lothlorien, meaning that whether Sauron reclaims the One Ring and tries to dominate their bearers, or whether the One is destroyed and all other Rings left weakened, then these elven havens would be left vulnerable: they'd have to be abandoned, even if the elves weren't already leaving Middle-Earth.
 * The Lindauzi of Warren Rochelle's The Wild Boy. They were regressing to a wild state without the Iani to bond with.
 * The L’Dira in The Lives of Dax, whose technology requires a resource their own world has run out of; now, they're wretched Planet Looters.

Live-Action TV

 * Battlestar Galactica Reimagined The Colonials are reduced to 50,000 survivors after the events of the miniseries. The society that forms with the surviving humans living aboard the handful of FTL capable ships that survived the genocide fall into this trope in three ways:
 * 1) Without the FTL technology, they would have been wiped out by the Cylons in short order.
 * 2) The technology for spaceflight; since the 12 Colonies are now radioactive wastelands and the only habitable worlds they find also get found by the Cylons shortly thereafter, without their ships the Colonials would not survive.
 * 3) The Battlestar Galactica itself; from the water filtration system that according to Commander Adama doesn't waste so much as a drop of water while cleaning a ship's supply of water to the ship's DRADIS that allows early warning of Cylon attacks or it's squadrons of Vipers and it's powerful weapon systems or the simple fact that none of the surviving civilian leaders are smart enough to keep the fleet together without Adama. This is proven early in Season 2 when the fleet is divided and the civilian fleet that left Galactica is prone to suicidal plans as dictated by their civilian leaders.
 * Star Trek has a fondness for this trope in its various series.
 * Star Trek: The Original Series episode "Spock's Brain". An underground civilization is coordinated by a humanoid brain called the Controller. When it fails, the inhabitants go looking for a replacement and acquire the title object.
 * TOS adored this trope, especially combined with Master Computer. Cue the James T. Kirk patented Logic Bomb!
 * Star Trek: The Next Generation had a society dependent on cloning run into Clone Degeneration. They were forced to do it the old fashioned way with a neighboring society of Luddites.
 * Star Trek: The Next Generation episode "11001001." The Bynar home planet is run by a computer which is going to be hit by an EM pulse from a nearby supernova and get erased, so the Bynars steal the Enterprise to temporarily house their computer's memory.
 * In Star Trek: Voyager, the Ocampa relied on the Caretaker and his relay to power their underground society, as well as keep them safe from the Kazon.
 * In another Voyager episode, a people created a stasis system that would keep their bodies in stasis and their minds active long enough for their world to become habitable again. As time passed, their fears became manifest in the reality as a clown that would bring out a guillotine when it was unhappy. Two of the people are dead before the crew finds them another one is killed in the process of saving them from it.
 * In another The Next Generation episode, the Enterprise encounters a ship from a planet that is suffering a species-wide plague that can only be staved off with a drug supplied by a neighboring race. However, this is revealed to be a ploy by the suppliers pushing a highly-addictive substance on unsuspecting people. Due to the Prime Directive, Picard agrees not to reveal the truth to the suffering race, but he also refuses to help them fix their few remaining ships (they have degraded technologically) under the same pretext, so that they will eventually be unable to trade with the other race and learn the truth after massive withdrawal symptoms.
 * Stargate SG-1 episode "Revisions", the computer was sending people to their deaths one by one as the power available fell below the levels required to support the population. It also altered their memories to make sure no one knew what was going on. Also interesting because the computer tricked the population into thinking they couldn't live without being constantly connected to it through an internet-like link, making everyone think they were even more dependent on it than they really were.
 * The Goa'uld are completely dependent on their queens to reproduce. Similarly the Jaffa are, for most of the early seasons, dependent on juvenile Goa'uld inside them.
 * In the Doctor Who story "Meglos", the people of Tigella live in a city where everything is powered by a single alien artifact, which gets destroyed at the story's climax; although they're initially horrified by having to manage without it, it's presented as ultimately being an opportunity rather than a disaster.
 * The 2007 Flash Gordon TV series featured Mongo as a Hydraulic Empire controlled by Ming, who had The Source, the only supply of drinkable water on the entire planet (except for the polar caps, which he controlled through a usurper in the polar regional government).
 * And that Source appears to be slowly running out. Which is why he's trying to develop interdimentional travel to.

Tabletop Games

 * The Computer in Paranoia, which was in part inspired by Logan's Run. In one adventure, when The Computer is destroyed Alpha Complex gets very dark, the air stops circulating, etc.
 * In Forgotten Realms, Drow culture is dependent on magical radiations so that cities were born and died when such deposits appeared and disappeared. Averted with vengeance in Sshamath, which managed to cross the deficiency period and emerge even stronger, having usual cheap solutions replaced with true arcane magic. This made it dependent on wizardry.
 * Most cities of Netheril were placed on artificial levitating islands. And when all magic was disabled for a minute or two... Since then, the relevant deity turns magic off "for maintenance" every few centuries, so no long-lasting civilization dares to depend on it that much.
 * In Warhammer 40000 the Imperium needs the Emperor to stay alive. He is using his psychic might to keep a hole in reality closed (that if allowed open would destroy the solar system, which is vital to the Imperium). He also plays a role in at least some psykers getting sanctioned, making them more powerful and giving them a little resistance against demonic possession. The Imperium depends on psykers he sanctions for faster than light communication. He also fights the chaos gods on their own turf. But most importantly he, he psychically calibrates the astromicon (which is pretty close to that hole in reality). The Imperium depends on the astromicon to make interstellar travel safe and reliable enough to be viable. In addition he is on a life support system called the Golden Throne, and its beginning to no longer work, and nobody save for the Emperor even knows how it works. Some fans actually think that if the Emperor dies: his spirit will continue to protect the Imperium from within the Warp, or be reincarnated. They almost always claim that he would do a better job of protecting the Imperium if he died.

Videogames

 * The plasmids from BioShock (series) fit this bill. Everyone used them, and they turn out to naturally hover between being Super and Psycho Serum (depending on which you took and if you abused them). Then a civil war breaks out and Ryan had them laced with mind control agents. So, needless to say, this terminally dependent society OD'd.
 * The Iifa Tree and the Mist from Final Fantasy IX are a mild example, because the heroes find an alternative energy source.
 * To a certain extent, the Lifestream from Final Fantasy VII.
 * OD-10 from Live a Live was in turn inspired by HAL.
 * The city of Lea Monde from Vagrant Story was designed as a city-sized spell. The game takes place long after the city has already collapsed on itself.
 * The quarians in Mass Effect live on a flotilla of ships in space, and are dependent on their giant greenhouse ships for all their food supplies. So much so that these are kept at the heart of the flotilla for their protection.
 * A bigger example is that galactic travel is impossible without the mass relays, If the various races took the time to develop their own means of Faster Than Light travel, it would solve a lot of problems.
 * This comes up in Mass Effect 2 -- the asari bartender on Illium complains that she became a laughingstock for suggesting they try to build their own mass relays.
 * When the Protheans decided to build their own Mass Relays, their one prototype may not have saved them but allowed them to save galactic civilization 50,000 years later.
 * High Elves and Blood Elves in World of Warcraft are dependent on magical energy, without which they become physically and mentally twisted husks called "Wretched". Night Elves suffer a similar affliction, but their need for magic is supplied by moonwells.
 * Goblins are somewhat dependent on kaja'mite for their superior intelligence. As the supplies have dwindled and they resort to more diluted forms, goblin society and technology has declined.
 * In Phantasy Star II, the terraforming on Mota and the carefree lifestyle of its people are dependent on Mother Brain for everything. Three guesses on what happens to her and what happens to Motavia in between II and IV.
 * In Armored Core For Answer, much of humanity (those who could afford it, at least) is dependent on the Cradle habitats they live in. One option the player can take later is to side with Old King and bring them down for the lulz. Maximillian Thermidor also wants to take them down, but this is because he believes that they are a temporary solution at best and that destroying them would open up the way for humanity to get to space.
 * In Star Control 2, the Utwig are highly dependent on the Ultron, a precursor artifact which gives them prophetic powers. When it breaks, the Utwig enter a perpetual state of mourning and are too depressed to do anything. Hilariously, everyone else is convinced that the artifact is absolutely useless. Whether it actually does anything is left ambiguous.
 * It is made clear that the Utwig are highly dependent on the Ultron simply because its breaking made them enter a perpetual state of mourning (since they were convinced of its power). This has nothing to do with whether the Ultron actually does anything, it's just that they didn't get the Ultron until shortly before breaking it, and that breaking happened at most a few years back.
 * The human population of Cocoon in Final Fantasy XIII depend on the Fal'Cie for everything. There are a few million Fal'Cie in Cocoon and each one handles a different function to keep the artificial world running. Among the Cocoon Fal'Cie we see in the game, there's a Fal'Cie in charge of running power plants, one that handles food production, another one acts as Cocoon's artificial sun, the Fal'Cie Eden, , and there's . Without the Fal'Cie  Cocoon would fall apart. The Pulse Fal'Cie on the other hand seem more geared towards terraforming Gran Pulse.
 * The world in Magna Carta II has unnaturally high levels of ambient magic, thanks to the Hero of Legend. It is specifically noted that with so much magic around, nobody has had to farm for food for at least a thousand years. The heros end up having to bring the levels back to normal and force society to labor for sustenance for the first time in generations, as it turns out that.
 * The first Fallout game starts with the main character being sent out of the Vault to find a new water chip, without which the Vault will run out of clean water.
 * This is actually true for all Vault populations. They are completely reliant on the technology of the Vault for their needs and any disruption in the service can be fatal.
 * The civilization of magic in Chrono Trigger is dependant on, well, magic. Unfortunately, their version of magic taps into the core of a planet-eating Eldritch Abomination, and their queen wants more and more of this power. This led to their downfall.
 * The civilization of magic in Chrono Trigger is dependant on, well, magic. Unfortunately, their version of magic taps into the core of a planet-eating Eldritch Abomination, and their queen wants more and more of this power. This led to their downfall.

Web Originals

 * Orion's Arm has a serious problem with people developing Baseline Hyperdependency Syndrome (that is: humans are spoiled rotten by the AIs) and nothing has even gone wrong yet, although many groups predict that collapse is imminent.
 * Neopets' Darigan Citadel was once a normal medieval town, until someone stole the magic orb fertilizing their crops. Now the land is about as fertile as a cinder block.

Webcomics

 * Mother in Dresden Codak: a world-assimilating AI/ Grey Goo /Singularity that provides everything Humanity asks for -- to point of making people unnecessary, irrelevant and progressively infantile. They go to the verge of extinction as life in the virtual worlds she/it provides takes precedence over breeding. When humanity finally goes to war with Mother, victory comes at a terrible cost: much of human history and culture dies with Mother, every human is blinded.

Real Life

 * There are a little over seven billion people on this planet; before the nineteenth century it was a few hundred million, reaching the one billion mark around 1800 and still less than two billion in 1900, and more doubled in the last 50 years. Without our advanced technology, most of us would die. Horribly.
 * The Haber process feeds a third of the world.
 * By extension, oil, whose production is believed to have peaked.
 * And all the monocultured staple crops such as corn and wheat. If disease or climate change devastates them...
 * Every society or species, real, imaginary, sentient or otherwise is terminally dependent on something, oftentimes something which is completely taken for granted. For example, all life on earth is highly dependent on a massive hydrogen guzzling fusion engine in the sky, which we call the sun. The difference between continued existence and annihilation usually hinges on how tamper proof and/or sustainable that something is.
 * Yes well in that case I'd say that the big fusion-plant running our solar system is at least fairly tamper-proof.
 * Electricity is a crux these days, as the Eastern Seaboard found out a few years ago. It is used in everything from communications and transport right on down to food preparation and recreation, and then one tree falls...
 * That's the gist of the Road to Olduvai Gorge. Around 2012, there is predicted to be worldwide electrical grid failures, sending us back to the Dark Age, "and the stone age is just around the corner".
 * As seen in Crippling Overspecialization, many animal species are terminally dependent on a specific food or environment, such as giant pandas (bamboo) and polar bears (the vanishing sea ice).
 * Easter Island. The palm forests were wiped out not by over-logging, but by introduced rats.
 * A government that takes advantage of this is known as a hydraulic state.
 * Raise your hands, tropers: how long could you stay sane if the internet up and disappeared?
 * Earthlike planets actually cannot support life without liquid water on its surface. If its parent star actually starts to leave the main-sequence stage, said planet's temperature will actually exceed that of the boiling point of water, and the results will be self-explanatory. Also, plate tectonics cannot exist without liquid oceans. Guess what happens in about 1 billion years!
 * This can happen to countries who rely on cash crop farming to support their economies, especially in developing countries such as areas of Africa in the form of cotton and rubber to provide for its citizens and cover its expenses.
 * The plight of bees worldwide has led many to speculate on how hard it would be for us to pollinate all the plants we rely on without them.