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Yu-Gi-Oh! VRAINS episode 1: "Link into the VRAINS"
Cyberse World is a hidden digital world in Yu-Gi-Oh! VRAINS, created and populated by sentient AI known as the Ignis. This world was under attack by the Knights of Hanoi, led by Varis. One of the Ignis, Ai, was able to keep its location hidden, before barely escaping "Cracking Dragon".
The Cyberse World was created by the Ignis, AI with free will, as a place of their own inside the internet, where no humans could reach it. And it is also the birthplace of the Cyberse Monsters.  The Ignis divided the duties of maintaining their world among themselves, each dividing Cyberse into their own territories. In Ai's words, the Ignis would never try harm humanity, and would rather live in their own world.
One day, Ai was fooling around the water domain with "Linkuriboh". Aqua warned Ai not to be playing around, since it was dangerous. Ai didn't mind, but he nearly hurt himself when he fell down a waterfall. Aqua scolded Ai, reminding he should behave like an Ignis. Earth was jealous, and demanded of Ai to stay away from Aqua, as he'd protect the latter. Ai, unlike other Ignis, had a human's instinct. Due to his rebellious behavior, Lightning observed him, believing that his disposition would inspire the other Ignis to evolve.
However, Dr. Kogami's simulations showed that, in a group, the Ignis would destroy the world, but separately, they'd improve humanity through coexistence. The exception to this was Lightning, who was predicted to demolish the others' progress and start a war between the Ignis and humanity. When Cyberse World was constructed, Lightning ran simulations at the same time Dr. Kogami ran his on the Ignis' future, and warned SOL Technologies of the threat. Since Lightning believed Dr. Kogami would soon learn that Lightning would be the source of the Ignis turning onto humanity, he went and infected him with a virus, causing SOL Technologies to imprison him and making him believe they punished him.
Five years before the start of the series, Varis assaulted Cyberse with "Cracking Dragon" with the intention to destroy it. The different Ignis that protected it were restrained by Varis and thus unable to stop the destruction of their world. However an Ignis that had not been trapped appeared and forced a disconnection of Cyberse from the rest of the network, thus forcing Varis out of Cyberse while keeping its location known only to him. However, Varis, furious by this Ignis' interference, ordered his "Cracking Dragon" to capture it, which led to the AI being dismembered by the monster's jaws. This made Varis and the Knights of Hanoi spend the following years searching for the Ignis' remnants in order to find the location of Cyberse.
Aqua spoke to Earth, telling him that Cyberse World would soon break apart. She asked of Earth whether he would join humans or the Ignis, to determine the future for the humanity and Artificial Intelligence. At first, Earth thought that Aqua was to admit his feelings towards her, but stopped when Aqua stated it was time to determine whether they should coexist with humans, or abandon them. Earth wanted to join the side Aqua chose, but the latter was also indecisive. Instead, Aqua had Earth find on its own whether they could trust humans. To help Earth, Aqua gave him the "Crystal Heart".
Lightning was designing the "Judgement Arrows" card, but Aqua noticed his activities. Lightning claimed the card would protect Cyberse World from humans, but Aqua found out he was lying. To prevent her from interfering, Lightning sealed Aqua in a cage. Aqua questioned his motives, while Lightning admitted he would destroy Cyberse World to further his actions.
At an unspecified time when Ai and Playmaker are battling against the Knights of Hanoi an unknown enemy breaks through Ai's program and starts an attack against the Cyberse world. Using Judgement Arrows, they discovered the realm's weaknesses and instantly destroy it. The Ignis evacuate the world to parts unknown, as Flame contacts Takeru Homura in the Human World.
Ai reopens the Cyberse after the threat of the Knights of Hanoi had been eliminated, but is devastated by the state he finds it in. Unable to find the other Ignis, Ai begins to panic before discovering Linkuriboh hiding among the ruins of the city. A conversation between Queen and Akira Zaizen seems to indicate SOL Technologies was able to locate the Cyberse World and realized the Ignis are missing.
Windy tried to reunite with the other Ignises. Thus, he started collecting data material and used it to create a place near LINK VRAINS. He believed the Ignis would learn about the territory and seek it out, as well as the enemies, whom Windy wanted to battle against. However, Lightning changed Windy's personality to be menacing and full of grudge towards humanity.
However, Lightning eventually revealed to Ai and Flame he was the perpetrator that was responsible for destroying the Cyberse World so he could "reconstruct" the realm, as well as to initiate his plans to fight humanity itself. Bohman the third generation AI constructed by the Lightning stated he also participated in the attack that destroyed the Cyberse World during the Tower of Hanoi incident with the use of Judgement Arrows  and with "Paradox Hydradrive Atlas" as per Lightning's demands.
According to Ai's flashback, Cyberse a is utopian paradise for the Ignis. Cyberse was once a barren land with a tower made of stone, strapped to the ground cables. As the Ignis evolved, so did their world. Cyberse, in its evolved state, is divided into six biomes outside a hexagonal out-layer with six cities on the points. The cities are connected by grasslands that outline a large city surrounding the pillar, which has been weathered down and now tethered to six, metallic pillars hovering above the outer cities with yellow spheres. The original tower is in the middle of a deep hole.
The setup of Cyberse shows the counteracting elements being across from one another as each biome represents a Monster Card Attribute: Fire (the volcano) is across from Water (the ocean), Wind (the valleys) is across from Earth (the mountains), and Light (the plains/desert) is across from Dark (the gorge).
When Varis invaded Cyberse, the world became dark with dark green clouds that block light and the hole around the tower is filled with lava, which started melting the tower. A large ring surrounds the tower.
When Ai returns to Cyberse, the world had been desolated into a barren wasteland with the central tower missing. The sky is red and with dark clouds and the pillars have been broken and fallen to the ground. The cities have been reduced to ruins and giant craters dot the land.
- ↑ Yu-Gi-Oh! VRAINS episode 11: "Neutralized"
- ↑ Yu-Gi-Oh! VRAINS episode 43: "The Reveal"
- ↑ Yu-Gi-Oh! VRAINS episode 45: "A Journey's End - Part 1"
- ↑ 4.0 4.1 Yu-Gi-Oh! VRAINS episode 67: "AI's Longing"
- ↑ Yu-Gi-Oh! VRAINS episode 73: "Light Blade that Slices Despair"
- ↑ Yu-Gi-Oh! VRAINS episode 96: "Lightning's Crime"
- ↑ Yu-Gi-Oh! VRAINS episode 98: "The AI that Crossed the Line"
- ↑ 8.0 8.1 Yu-Gi-Oh! VRAINS episode 1: "Link into the VRAINS"
- ↑ Yu-Gi-Oh! VRAINS episode 66: "Earth Ignis "Earth""
- ↑ Yu-Gi-Oh! VRAINS episode 74: "Captured Ignis"
- ↑ Yu-Gi-Oh! VRAINS episode 47: "Playmaker Returns"
- ↑ Yu-Gi-Oh! VRAINS episode 55: "To the Unknown World"
- ↑ Yu-Gi-Oh! VRAINS episode 97: "Ignis Unification Plan"
- ↑ Yu-Gi-Oh! VRAINS episode 71: "Declaration of War"
- ↑ Yu-Gi-Oh! VRAINS episode 72: "Clear Perfection"
- ↑ Yu-Gi-Oh! VRAINS episode 94: "Raging Soul"