Vicious Cycle

""Harman, the world never changes. All it ever does... is turn.""

- Kun Lan, Killer 7

""That's why they're called revolutions. They always come round again.""

- Samuel Vimes, Discworld

Every 1,000 years, the Powers That Be arrange a major event. It may be The End of the World as We Know It (and its subsequent rebuilding) or merely a threat of one, a mass mind-wipe, or it may be something that involves a Chosen One, who is supposed to do something predefined, or the whole effort will derail.

The reasons why they do so varies greatly. It may be necessary to keep a Sealed Evil in a Can dormant (which often involves the Chosen One's sacrifice), to uphold the Balance Between Good and Evil or the Masquerade (in other words, to prevent either side from winning too much or knowing too much). Alternatively, the organizers may do it purely for entertainment, or it may "just happen" Because Destiny Says So, with no further explanation.

The bad news is, last time this happened was exactly 999 years and 360 days ago, and our heroes become involved, usually against their will, in the next iteration. Two outcomes can possibly occur: either they accept (or are forced to accept) their destiny and continue the cycle, or they reject it. The former case is risky because fans are likely to dismiss the story as "pointless"; in the latter, what happens next depends on the show's position on the Sliding Scale of Idealism Versus Cynicism, which can mean either a happy ending, in which the cycle is broken for good, or a Downer Ending. If multiple factions want a say in this process it can result in a Tournament Arc or There Can Be Only One.

Regularly-Scheduled Evil is a special case of this.

Anime & Manga

 * In Mai-HiME, the "HiME Carnival" occurs every 300 years, and failure to comply would result in The End of the World as We Know It. There is a subversion, as it is not Mai herself who ends the cycle, but rather.
 * Implied in Wolf's Rain though not stated in so many words.
 * Berserk's Eclipse, which goes down every 216 years, marks the birth of a new member of the Godhand, which involves the sacrifice of a whole lot of people, and the gathering of every demon in the Berserk universe for a great feast. The most recent occurrence of this happens at the end of the anime when.
 * In addition, there's the even rarer Incarnation Ceremony, which happens only once every thousand years, and which allows a member of the Godhand to be incarnated into a fleshly form. The most recent occurrence of this happens in the manga, when.
 * Genesis of Aquarion has the Shadow/Fallen Angels who come back every 10,000 years or so to threaten the Earth, although the cycle is broken during the series itself.
 * This Ugly Yet Beautiful World: the goddess of death and destruction comes back to cause yet another mass extinction on Earth.
 * Gash Bell: The battle to become Mamodo King occurs once every 1,000 years. As it is shown, the participants frequently have their lives ruined to some degree as a result, and a lot of innocent people get caught up in it.
 * Queen Millenia: If the title isn't enough indication, for every 1,000 year period, a woman from the planet La-Metal is sent to secretly rule over the Earth and lead the underground organization that secretly controls the entire planet.
 * In Otokoyo,

Comic Books

 * In the comic book Miniseries Seven Soldiers, the Sheeda wait until mankind has reached a certain point of technological advancement before swooping down and harvesting their technology, effectively 'resetting' mankind and forcing them to start from scratch.

Film

 * In The Matrix, the Machines destroy Zion and (with the help of The One) reboot the Matrix every 100 years, to prevent the Zion "anomaly" from expanding uncontrollably. Neo is the first One to refuse to participate in the reboot, and later strikes a peace agreement with the Machines, saving Zion and ending the war.
 * The movie The Dark Crystal had "The Great Conjunction" of the world's three suns, the time of prophecy when a destined, Last of His Kind hero is fated to restore the balance of the planet. It's noted in the film that every time a Great Conjunction rolls around, something big happens. This can be good or bad (the last Great Conjunction had the Dark Crystal being broken, thus starting everything in the movie). Eventually, the "something big" might even be the destruction of the entire world.
 * The Fifth Element: an evil planet comes to life every five thousand years and attempts to collide with Earth, causing a chain reaction that would destroy all life in the universe. This can only be prevented by the use of an ancient superweapon and, in the film, The Power of Love.

Literature

 * The Lord Of The Isles series by David Drake. The powers are building to a thousand-year peak. Ordinary wizards find themselves with out of control powers that brought down the kingdom during the last peak. In its current shattered state another such error will destroy civilization.
 * In Stephen Baxter's novel, Manifold Space, the Galaxy works on a so-called "Reboot cycle", where life, intelligence and civilizations appear practically everywhere in some form (that is, even as lichen colonies on the surface of stars, or giant crabs living of rogue planets). These civilizations advance, and begin a bubble-expansion at increasing speed. From there, the bubbles either collide resulting in omnipresent wars, or collapse in on themselves when they hit the lightspeed barrier and can no longer sustain the expansion. These events lead to massive technological backsteps and extinction events (which is why everyone is bound by lightspeed; nobody has time to get really smart). In addition to this, each cycle ends with the Galaxy getting sterilized by colliding neutron stars releasing massive amounts of radiation, blasting everything back to pondscum.
 * The protagonists actually fail to prevent the current cycle from completing, but succeed in buying some time for the next iteration of the cycle by building a massive solar sail that would stop a neutron star collision.
 * In the novel Decipher, the sun reaches its peak resonance every 12 millennia, causing The End of the World as We Know It due to the solar flare from Hell. To avert it, the heroes have to reach Atlantis so it can quasi-crystallise the planet to protect against the gravity wave.
 * What? What? What?
 * In Stephen King's It the eponymous monster manifests itself in Derry every 27 years or so.
 * Likewise, in Wolves Of Calla the wolves visit Calla for harvest every 30 years.
 * In the Wheel of Time series, the eponymous Wheel is a metaphor for seven distinct ages, each of which ends after several thousand years. The last (Second) Age ended in the Breaking of the World, and the Third Age is prophesied to end similarly; presumably this happens every age. More sinisterly, Ishamael appears to have been meddling on a smaller scale this Age--about a thousand years after the Breaking, he sent the Trollocs to ravage the world, and another thousand years later he triggered the "War of the Hundred Years" by preventing Artur Hawkwing from having a living heir. (It looks as if his intent was to keep the technology level down.)
 * In The Mote in God's Eye,
 * In J.V. Jones's "Cavern of Black Ice,"
 * Politics in Dragaera are dominated by the Cycle, a predictable sequence by which each of seventeen Dragaeran Houses takes a turn governing the Empire. Each House's members have strengths that allow it to supplant the previous one, and weaknesses which will eventually allow its successor to claim the Imperial throne in turn.
 * In the Isaac Asimov short story "Nightfall", a world with six suns, at least one of which is in the sky at all times, has all its suns set simultaneously once per set period of time. Since the inhabitants have never seen the stars and have no clue they even exist, the sight of the night sky causes everyone to go mad and start burning everything to generate whatever light they can, returning civilization to the stone age.
 * Discworld's Death references this.
 * In Frederic Brown's story "Letter to a Phoenix", the entire plot is a man telling about how humanity repeatedly destroys its own civilization and has to start anew every 30,000 years or so - therefore, while all other races reach their peaks and after that must decay and die, humanity can survive forever - thus making it the eponymous Phoenix.
 * Dragonriders of Pern: The Red Star approaches Pern every 200 years and rains hungry Thread on civilization. The few occasions when it does not do this are termed Long Intervals and end up being an important clue to saving Pern from thread forever.
 * Memory, Sorrow, and Thorn: The Conqueror Star is a long-period comet (at least 500 years, although it seems to vary) whose coming universally heralds the end of an empire. The story opens at the beginning of a unique cycle in which the comet will appear in three consecutive years. This is, of course, the time that the Sealed Evil in a Can Storm King chooses to make his return.

Live Action TV

 * In Babylon 5, the Shadows launch a destructive war every thousand years, which the Vorlons help to put down. In the series, the protagonists object to this arrangement, and try to put a stop to it.
 * "All of this has happened before, and all of it will happen again."
 * Explained more explicitly in recent episodes as

Music

 * One of the major theme's of Pink Floyd's The Wall is the vicious cycle of isolation.

Radio

 * The Doctor Who audio dramas set in the Divergent Universe weave together a plot of cyclical existence: in fact, the reason the universe has no Time is because no moment has a unique existence to anchor the Time Vortex to. Or something, it's kind of convoluted.

Tabletop Games

 * In the Villains and Vigilantes adventure Devil's Domain, every 666 years the Earth's dimension and Hell come close enough together for the Devil to create a bridge between them that will allow his demon horde to pour through.
 * The Aurora in Magic: The Gathering's Lorwyn and Shadowmoor settings, which changes one world to the other (and the minds of those within). Its eventually revealed to be a magically slowed down
 * Dungeons and Dragons
 * Planescape setting. Every 289 years (17 cycles of the gears of Mechanus) the Great Modron March starts. It consists of a horde of modrons traveling around the Great Ring, causing devastation as they pass.
 * Supplement Treasure Maps, adventure "Sign of the Times". Every 700 years during a specific astrological conjunction of planets, moons and stars the king of a desert empire will fall ill and die, and his son will take his place. The new king will become evil and cruel, raising taxes and invading other countries. Natural disasters (famine, pestilence and drought) will ravage the land.
 * In Earthdawn and Shadowrun, the Horrors return to Earth from astral space to torment and ravage its living creatures every few thousand years.

Video Games

 * Shin Megami Tensei is very big on this, given the emphasis on the Order Versus Chaos setting, the instability of Neutrality, and the constant reminder that Humans Are Bastards. Particular examples include the Conception in Shin Megami Tensei Nocturne, the Schwartzwelt in Strange Journey, and the constant rise and fall of several of the series' gods. It's a bitter reminder that Order Versus Chaos cannot be anything except a Forever War.
 * Dark Gaia of Sonic Unleashed gathers energy over millions of years, then rises and destroys the planet. This is counterbalanced by Light Gaia, who puts it all back together. Dr. Eggman's attempt to harness the energy of Dark Gaia ends up causing a smaller scale version of this in that the planet is split into floating continents, due to Dark Gaia not being at full strength thanks to the early awakening.
 * In the Phantasy Star series, the Dark Force attacks the planets of the Algol system every 1,000 years. In Phantasy Star IV, this is revealed to be due to the fact that
 * Not only that,
 * Final Fantasy X has Sin, whose cycle is a little flexible - when destroyed, he rises again in a few years, but the amount of time he's active depends on how long it takes a summoner to perform the "Final Summoning" and defeat him.
 * Tales of Symphonia has a similar situation, although it isn't clear if it's quite as regularly timed as most others.
 * It's supposed to be. The Chosen is sent on his/her journey to supposedly reawaken the sleeping Goddess; doing so will revive the land and banish the evil Desians. What it's really doing is controlling the distribution of the remaining mana and preventing anyone's technology from getting to the point of large-scale, advanced war. It's supposed to happen at a fairly regular rate, but thanks to the Renegades killing a Chosen before the journey was completed, Tethe'alla's technology was allowed to get far more advanced than it should have.
 * That world has a larger scale vicious cycle going as well. First, magitechnology is developed. Then, they develop a Mana Cannon. Use of the cannon uses up so much mana that supplies run low, chaos ensues, war escalates due to the combination of scarce resources and advanced weaponry, and humanity is thrust back to the dark ages, often with the help of an external force (usually malicious angels, although at least one meteor). Then, after a thousand years or two, people exploring ruins begin finding out about this neat thing called "magitechnology"...
 * The latest story intel on the Starcraft series (mainly the "Dark Templar" book trilogy) posits that the Xel'Naga are not merely a superadvanced civilization whose experiments with creating the Zerg and Protoss failed miserably leading to their extinction. Rather, both the Protoss and Zerg are exactly what they were required to be, and in time the two species would have come together to create the new iteration of the (essentially godlike, "star-forging") Xel'Naga, as part of a cosmic cycle stretching back to the dawn of time. The current cycle never came to completion as intended, however, because someone interfered with the Zerg's genetic programming, making them savage and all-consuming, as a first step to breaking the cycle and ending the Universe.
 * The eponymous castle of the Castlevania series of video games, as well as its lord, Count Dracula, reappears every 100 years in a different form. In fact, one of the major plot points of Castlevania: Symphony of the Night is that Castlevania's latest appearance is way ahead of schedule.
 * Castlevania 2 revolves around the player having to revive Dracula ahead of schedule in order to kill him again, in order to break a curse he put on Simon Belmont for defeating him.
 * And the there's Aria of Sorrow and Dawn of Sorrow,
 * Castlevania: Portrait of Ruin is another one that interrupts the vicious cycle. With the onset of World War II,
 * The four Sinistrals, villains of the Lufia series, are reborn every 100 years... a cycle which can only be broken if Erim, Mistress of Death, is the last one killed.
 * Mass Effect's plot revolves around this. Archaeologist Liara T'Soni talks about clues she has found during her research that indicate that every time a civilization has reached a certain level of technological development, it has been violently destroyed, and the next civilization has been founded on technology scavenged from the ruins. Commander Shepard eventually discovers that . The game's storyline revolves around Shepard's efforts to prevent the cycle from recurring again.
 * It gets even more frightening in Mass Effect 2 as . And to make things even worse, we also find out that.
 * Many of the abandoned/uncolonised planets in the game have flavour text. In quite a few of them, it will say: There is evidence that sentient life once inhabited this planet. They were obliterated by a sustained, organised and totally destructive orbital bombardment. Every one has the estimated date of the destruction as a multiple of 50,000 years.
 * In Mass Effect 3, we find information that furthers this theme:
 * In the computer game Myth: The Fallen Lords and its sequels, it is stated that . Sounds bad? That's not all. . Thankfully, the games imply that events in the previous iteration of the cycle may have allowed Alric to break the cycle for good, or that 's actions in the sequel may have resulted in this. We don't know for certain, though.
 * Sid Meier's Alpha Centauri uses this one nicely to explain why the game ends after 500 turns. Turns out every 100 million years, Planet's native life grows into a full-fledged, planet-wide hive mind, but the growth is so explosive it ends up eating everything on Planet and thus destroying itself. When the UN Unity arrived there, it's already been 99,999,500 years since the last outgrowth, and humanity has just 500 years to stop this cycle! What a pisser! There is also some implication that the thoughts of the human colonists are playing a role in awakening Planet and pushing it towards the end of the current cycle faster than it normally would.
 * The Alien Crossfire Expansion Pack introduces the descendants of the Precursors that created Planet. It is also mentioned that a previous attempt by the creators to activate the final stage of the "Flowering" on a planet in Tau Ceti resulted in The End of the World as We Know It for them, with their descendants losing much of the knowledge their ancestors had. Presumably, similar catastrophes resulted from the other four experiments. Chiron is slecifically called by the aliens "Manifold Six". One of the factions wants to use the Flowering to attain godhood at any cost, while the other one wants to maintain Planet's self-destructive cycle, avoiding another Tau Ceti disaster.
 * Killer 7 reveals at the end
 * Septerra Core subverts the trope somewhat in that the prophesied date on which all of the planet's layers go into a position that allows access to the core is still many years away. Drama is provided by the antagonist destroying layers and messing with the planet's clockwork so that he can access the core during his lifetime.
 * Oblivion in the Elder Scrolls series has this in the form of Sheogorath.  The player, however, has the chance to end this cycle forever.
 * Every 60 years in Touhou Project's Gensokyo, there's a surge of death for whatever reason. Of course, since Death is The Slacker, instead we get lots and lots of flowers everywhere.
 * Actually the surge of death is in the outside world (can you guess why Japan had so many ghosts in 1945?) The unnatural flower bloom comes from the fact that there is no room for all the new ghosts flowing in.
 * Dragon Age II is built on the Vicious Cycle between mages and the templars meant to keep them in check. To keep them in check, the templars lock mages away in towers and generally treat them as less than human beings. To break this oppression mages turn to Blood Magic. This causes the templars to become more oppressive and by the end of the game both have reached the breaking point and the world is about ready to go to war between the mages and templars. Which side exactly started the cycle is never answered and aids the game's Grey and Gray Morality.
 * The Grail War in Fate/stay night occurs every 60 years, when there is enough magical energy in Fuyuki to activate the Grail. The system was arranged many years ago by the three mage families in order to determine the Grail's possession. The thing is, the war was supposed to have ended on the fourth iteration, but it's eventually revealed that the process merely sped up, allowing the next Grail War to start fifty years early.
 * The Legend of Zelda's Hyrule suffers this chronically, albeit not on a very tight schedule with Ganondorf/Ganon being repeatedly sealed and escaping or dying and reviving/being reborn exactly the same. Even when Ganon doesn't show up, another powerful demon will emerge to cover for him due to.
 * In Monster Girl Quest, the human goddess, Ilias, has forbidden sexual intercourse with monsters. Seems fair enough, right? Well, all monsters are female, so if human males follow Ilias' commandment, it's genocide. So all the surviving species have adapted to raping human males every chance they get. Which, of course, leads the humans to believe all monsters are evil, which makes them more inclined to obey the commandment.

Web Comics

 * The calendar in Wapsi Square puts the world through cycle after cycle, resetting time every time it hits 2012. One character retains her knowledge through all cycles, and has seen over 80,000 years worth of this cycle.

Web Original

 * In the Whateley Universe, a mundane version of this happens with no less then three villains! Deathmaiden dies and returns almost exactly 20 years, and Diane Castle quotes this almost exact trope!
 * http://crystalhall.org/chboards3/index.php?t=msg&th=1543&start=0&S=f768b1cbdfbb06d0f615103540bbc4ef
 * The Necromancer 'arranges' a death every so often, only to return under a new ID. Furthermore, Deathlist, the rival of the Principal, always pulls a Villain: Exit Stage Left, only to return an indeterminate amount of time. These two may fit another trope as well.

Western Animation

 * So many in Xiaolin Showdown that it is pretty much a Running Gag.

Real Life

 * Ice Ages happen every once in a while. It always brings a massive extinction wave and the birth of new species.