Time and History (Avatar Supplement)
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10,000 years BA (before Aang's birth): The Avatar cycle begins
Roughly 10,000 years before the start of Avatar: The Last Airbender, the world was a misty wonderland of spirits, humans, and the Lion Turtles, the last of whom were tasked with protecting humanity. It was on their mammoth shells that humans huddled together, venturing into the spirit wilds beyond only when necessary. To protect them on those occasional journeys, the Lion Turtles granted humans the power of bending for the duration of their time in the wilds. The system was broken, however, when a human named Wan used firebending for selfish ends, and was banished to the wilds in punishment.
His exile became a journey in which he encountered Raava, the primordial spirit of light and peace, and Vaatu, the spirit of darkness and chaos. Wan, tricked into freeing Vaatu, merged with Raava in an effort to undo his mistake and keep Vaatu from flooding the world with malice. They succeeded, and their bond was made permanent, making Wan the very first Avatar. Thus empowered, Wan sealed off the polar portals that linked the spirit and the human worlds. In so doing, Wan created the foundations for the world of Avatar as we know it, and set out to safeguard its future.
1,000s of years BA: The four nations form
Thousands of years passed between the era of Wan and that of Avatar: The Last Airbender's heroes, in which the four nations as fans would come to know them coalesced into their familiar shapes. The Water Tribe, originally concentrated in the North Pole, split into two nations, with a splintered third settled in the Foggy Swamp. Centuries of tribal warfare, fortress-building, and subterranean exploration created the Earth Kingdom, united under a single monarch. The Sun Warriors, who would go on to teach Aang and Zuko the Dancing Dragon form, grew, declined, and finally settled into the obscure existence glimpsed in "The Firebending Masters," while the archipelago that would become the Fire Nation was brought together during the Unification Wars. In the midst of this upheaval, bending, once possible only through the Lion Turtles, was rediscovered and refined. Firebenders learned through observing dragons, waterbenders through studying the tidal pull of the moon, airbenders through their bonds with the sky bison, and earthbenders through the tunneling of badgermoles. Forms, disciplines, and styles were created, explored, and advanced, from lightning generation to literal flight, in the case of the legendary Guru Laghima. Though many years of this era are heavy with warfare and famine, so too are they bursting with exploration, adventure, and spirituality.
300 years BA: The era of Avatar Kyoshi 300 years prior to the events of Avatar: The Last Airbender, Avatar Kyoshi rose to power. Though she would become a formidable enforcer of justice, she was born to an infamous pair of criminals who left her in the care of strangers who, upon learning of her parents' eventual death, abandoned her on the streets to starve. Years of deprivation, study, and conflict ensued, molding Kyoshi into an Avatar as celebrated as she was feared. Her most well-known exploits happened later in her reign: the creation of Kyoshi Island and the founding of the Dai Li, the cultural authority of Ba Sing Se who, by the time Aang encountered them, acted as a brutal secret police force. The former event, in which she bent the earth down to its magma to split off the tip of a peninsula and make it an island, was to keep the village located there safe from Chin, a fearsome conqueror. The latter act was in response to a peasant uprising, and would go on to be seen as one of Kyoshi's greatest mistakes. She was a complicated figure, her legacy up for debate from all corners, but there is no disputing the massive effect she had upon our heroes, centuries after her death.
100 years BA:The era of Avatar Roku
When Kyoshi's long life finally came to a close, the next Avatar was born: Roku, a noble son of the Fire Nation. Growing up beside Sozin, his best friend and heir to the throne, his life was largely untroubled until he was revealed as the Avatar as the age of 16. Years of training ensued, during which Sozin became Fire Lord — and yet the two remained as close as brothers. They reunited, reconnected, and when the time came from Roku to marry, it was Sozin who acted as best man.But Sozin's ambitions had grown with every passing year. He revealed his plans for world conquest to Roku, who was horrified, no matter how benevolent Sozin claimed his intentions to be. The two split, passing decades without contact. When the volcano crowning Roku's island home erupted, Sozin did rush to his friend's aid — only to let him die in the ashes, upon realizing that Roku's death would allow him to carry out his vision of globe-spanning rule. Hundreds of miles away, a boy named Aang was born in the Southern Air Temple, heedless of the Fire Lord's intentions and the mess they would make of his childhood.
12-112 years AA: The Hundred Year War
Aang proceeded to spend 100 years in the ice, leaving the world without an Avatar in its time of greatest need. Fire Lord Azulon succeeded Sozin, continuing his campaign of conquest with bloodthirsty zeal. The Southern Water Tribe was devastated during these years, subject to an assault that destroyed their central city, kidnapped their waterbenders, and led to decades of violent raiding which would eventually claim the life of Kya, Katara and Sokka's mother. The Fire Nation's attempts to destroy the Earth Kingdom went less smoothly. Though enormous swaths of the nation were indeed decimated, subjugated, and put under Fire Nation control, Ba Sing Se, the legendary capital city, resisted capture. General Iroh, crown prince of the Fire Nation, had received a vision in his youth that appeared to bode well: Himself, conquering Ba Sing Se at last. Empowered by this prophecy and at the apex of his legendary skill, he laid siege to the city's outermost wall with all the might of the Fire Nation army behind him.