When It All Began

"What was the start of all this?

When did the cogs of fate begin to turn?

Perhaps it is impossible to grasp that answer now

From deep within the flow of time..."

- Chrono Cross opening text

A single very significant moment, related to the fate of every single main character, and driving the entire plot, that happened before the beginning of the story.

That event will probably be discussed, interpreted, viewed through flashbacks, and a The Reveal might show its true meaning later. In cases where the characters have any way of interfering with the past, this event will be their target.

Since these these events are more exciting, and more detailed than your average background story, they are frequently used as the setting for a Prequel.

The lines "Everything started x years ago", or "It all began when..." are very likely to be uttered.

See also Great Offscreen War.

Anime & Manga

 * Naruto, where the Fourth Hokage seals the Nine-Tailed Fox into a baby (the titular character) when the Fox attacked Konoha. The act cost the beloved Fourth Hokage his life, which becomes very significant later on. Later, we learn that
 * The Big O: The disaster forty years earlier that destroyed civilization and caused universal amnesia in the inhabitants of Paradigm City.
 * In Neon Genesis Evangelion, the Second Impact.
 * Haruhi Suzumiya: "Three years ago", something paranormal happened, possibly the universe was created, or at least most of the main characters were retconned into existence. It's also a recurring time travel destination.
 * Higurashi no Naku Koro Ni: The curse of Oyashiro-sama. Either the first death five years prior to the story or Satoshi's disappearance one year prior.
 * Umineko no Naku Koro Ni:
 * Dragonball has several of these, including the arrival of a lone Namekian on planet Earth and the destruction of the Saiyan homeworld.
 * Nabari no Ou: The "incident ten years ago", when the Shinrabanshou was used.
 * The execution of Gold Roger, triggering One Piece's great age of piracy.
 * Steins Gate
 * In Code Geass, the invasion of Japan, and the attack on Lelouch's family.
 * In Dennou Coil, there are three of these, five years ago, four years ago, and one year ago.
 * In Inuyasha everything happened because of events from 50 years ago.
 * In Fullmetal Alchemist, Edward and Alphonse's disastrous attempt at bringing their mother back to life through human transmutation, and the Ishvalan War, which takes place a little bit before the former incident.

Film

 * The heist in Reservoir Dogs.
 * The oft-alluded-to discovery of warp flight and how it started the brand-new era of space travel in the Star Trek verse, actually becomes the setting of the not-quite prequel Star Trek First Contact. That movie also uses the first attempted Borg invasion as a second kind of backstory.
 * The Original Series episode "Space Seed" was the When It All Began for Wrath of Khan.
 * Avatar starts with a narration by Jake Sully explaining how he wound up on Pandora. His twin brother Tom was supposed to go on an expedition to the planet, except he died in a grocery store robbery beforehand. The mortician who burns his body at the start of the film recommends as he does so that Jake go to Pandora himself for a fresh start.

Literature

 * Treasure Island: Captain Flint buried his treasure on the island.
 * From Harry Potter, The first war with Voldemort, particularly the death of the Potter parents, Harry's marking, and Voldemorts downfall, all in a single scene.
 * Robert's Rebellion from A Song of Ice and Fire.

Live Action TV

 * in the revived Battlestar Galactica Reimagined.
 * Earth: Final Conflict begins three years after the arrival of the Taelons.
 * Khitomer in Star Trek the Next Generation, as it had a profound effect on many of the characters, and the empires themselves.
 * The Cardassian occupation of Bajor in Star Trek Deep Space Nine. Almost all the non-Starfleet characters participated and lived through it, and many of the Starfleet characters were involved as well.
 * The Time War in the revived Doctor Who.
 * Somewhat coyly alluded to in the twentieth anniversary special, ''The Five Doctors": "So you're going to go on the run from your own people, in a rackety old TARDIS?" "Why not, that's how it all started!"
 * War of the Worlds (1988-1990) took place 35 years after the Martian invasion depicted in the 1953 George Pal movie.
 * Firefly has this with the Unification War.
 * Lost's antepenultimate episode, "Across the Sea," was a Whole Episode Flashback to the birth of Jacob and the Man in Black, revealing how they came to be who they are, which set in motion events continuing 2000 years into the future.
 * Kamen Rider W has the "Begins Night", the case in which Shotaro accidentally caused the death of his mentor, met his future partner Philip, and became Kamen Rider Double for the first time; it also qualifies for Philip because it marks the point where he starts taking responsibility for helping make Gaia Memories. They actually use the term as a shorthand for this trope later on; when they meet Ryu Terui, Philip comments that the murder of his family was his own personal Begins Night.

Music

 * In The Protomen, Act II, the Prequel, details how Dr. Wily took over, setting up the events of Act I.

Video Games
"Rucks: "A proper story's supposed to start at the beginnin'... this one ain't so simple.""
 * The formation of The Philosophers in the Metal Gear franchise.
 * Also the Boss's last wish:, which was shown in Metal Gear Solid 3, a prequel. Big Boss's and Zero's differing interpretations of that wish and how to fulfill it lead to almost everything that happens in the rest of the series, including the creation of Outer Heaven and the creation of  , which leads directly to the events of Metal Gear Solid 2 and 4.
 * The DL-6 incident from Ace Attorney.
 * In Investigations the KG-8 case fills a similar role for the new characters.
 * The IS-7 incident in Investigations 2 links everything together even moreso,
 * Ghost Trick has the incident in Temsik Park 10 years ago.
 * Fate Stay Night: The last Holy Grail War 10 years ago, especially its final battle.
 * Although it's not really apparent until the end of the series, pretty much everything that happens in the Metal Gear universe has its roots in
 * Final Fantasy XIII has the 13 days prior to the start of the game in flashbacks throughout the main game, which manages to link all of the main characters to the plot by way of a single event.
 * What happened in Nibelheim five years prior to the events of the game in Final Fantasy VII.
 * In Final Fantasy VIII, the Sorceress' War, 18 years before the game takes place, sets off the events of the game, though due to Time Travel, the beginning point is itself affected during gameplay.
 * The Legend of Zelda Skyward Sword
 * In Metal Walker, the Rusted Land is the way it is due to an accident 50 years ago.
 * Almost all the events of the Knights of the Old Republic games can be traced to Revan and Malak leading roughly half of the Jedi to fight in the Mandalorian Wars. And much of that can be narrowed down to the Battle of Malachor V, especially in the sequel.
 * Bastion's Calamity happens just before the game. Rucks says it best;


 * Mass Effect has Shepard's visions from the Prothean Beacon lead them to Ilos, the location of the underground base where the last Prothean scientists worked and ultimately sacrificed themselves to delay the Reaper invasion of Shepard's time.
 * The third game has Shepard return to Eden Prime, the location where they first had their vision.

Webcomics

 * Drive: If it weren't for the fleeing pre-maker's actions, humanity wouldn't have gained access to the Ring Drive.

Western Animation

 * The extinction of the Air Nomads and the disappearance of the Avatar occurs 100 years before the beginning of Avatar: The Last Airbender.
 * Re Boot season 4 gave several flashbacks to before the series began. These explained the origins of Megabyte and Hexadecimal and how the main characters were involved in it. A mix of Nice Job Breaking It Hero from Bob and a Gone Horribly Wrong from Dot kickstarted everything.