Tower of Hanoi
The Tower of Hanoi was a data construct created by Kiyoshi Kogami to destroy LINK VRAINS in an effort to destroy the Ignis. It was born from a seed that Kogami and Varis planted in the depths of LINK VRAINS, and functioned by absorbing data of all kinds to then release it in a surge that would have annihilated the entire Internet and everything connected to it.
Once the seed, which resembles a glowing blue cube, is planted, the Tower of Hanoi begins absorbing data from its surroundings, resembling an angry red ball of energy with tentacles. Once it has absorbed enough, it grows into a massive series of "roots" that connect in a central shaft as an antennae linked to the global network. As the tower grows, the core rises with it and it continues to glow, with two short branches beside it resembling a cross. As the core rises, it causes grey rings to surround the shaft; according to Kal Kolter, these are made of absorbed data, including those of the Avatars present at its activation. The affected Avatars are prevented from logging out, and if nearby users are defeated in a Duel, their data is also absorbed and added to the Tower. The data is absorbed at a rate fast enough to complete a ring every hour; once a ring is completed, it fills with magenta data. Once all six rings are complete, the data will be released in a surge that would destroy the Internet and everything connected to it. It would also cause mainframes to become EMP devices that would destroy any machine in range, preventing data stored offline from being preserved. Data Storms summoned near the Tower are more violent than normal. The top of the tower branches out and is surrounded by fused growths. Two of these growths contain dirt platforms, where Playmaker and Varis have their final Duel.
Following the Tower's modification into a scanner, a pentagram composed of the tattoo on Ryoken's hand appears on the ground and causes red lightning to spread through the Tower, turning it blue and causing it to generate rings of light. When the Tower is activated, the rings concentrate into the central shaft and the Tower releases a massive surge of blue energy.
Varis and Dr. Kogami planted the seed of the Tower in the sewer system of LINK VRAINS, where they planned to have it absorb the waste data that flowed through it to allow it to grow. Ghost Gal and Kal Kolter both detected the Tower's core growing in the sewers due to an anomaly that it caused. Ghost Gal found the core first, analyzing the core and realizing that it contained a massive quantity of energy. She was discovered by Varis, who forced her to Speed Duel him to escape, and asked about the core during their Duel, but she didn't get a concrete answer from him. She was defeated and her data added to the core, but she gave the data that she had collected to Playmaker before her absorption.
Varis released the Tower, absorbing a large portion of LINK VRAINS and many nearby Avatars. Kitamura logged into LINK VRAINS to ally with the Knights of Hanoi, but he was defeated in a "test" by Specter and his data was added to the Tower. Playmaker, The Gore, and Blue Angel logged into LINK VRAINS to stop the Tower, agreeing to an alliance before making their separate ways to the Tower. Blue Angel was the first to encounter opposition, Dueling Specter. She was defeated and her data added to the Tower as it completed the first ring. Her brother, Akira Zaizen, logged into LINK VRAINS and rushed to her, but he was captured by Dr. Kogami, and helplessly watched his sister's absorption. The Tower continued to corrupt LINK VRAINS, even destabilizing the bridge that Playmaker and Specter were Dueling on and forcing Specter to reinforce it with his "Sunavalon" monsters. Specter attempted to prevent his loss by threatening to infect Zaizen with a virus that would allow the Tower to absorb him, which worked for a while until Zaizen sacrificed himself and his data was added to the Tower. Playmaker brutally defeated Specter, who was purged by Varis to prevent the Tower, which had just completed its third ring, from absorbing him.
With three rings of the Tower completed, The Gore arrived at the foot of the Tower, but was opposed by Varis, who defeated him in a Master Duel. Playmaker arrived during the Duel, as did Frog and Pigeon. After the Duel, Playmaker and Varis were left as the only Duelists in LINK VRAINS, and the fourth ring was completed. Playmaker and Varis Speed Dueled in the Data Storm that the core was generating in the rubble of the fifth ring, during which Varis revealed the origins of the Ignis to Playmaker. They both had difficulty using their "Storm Access" Skills in the dense Data Storm of the core, but were able to eventually access it; Playmaker with Ai's assistance, and Varis with Dr. Kogami's. However this effort exhausted Kogami, whose body perished, and Varis ended the Duel in a draw with an explosion so great that it logged them out of LINK VRAINS instead of allowing the Tower to absorb them.
Immediately afterwards, the fifth ring of the Tower was completed. Yusaku was able to confront Varis in the real world at his home, and they logged back into LINK VRAINS for a final Master Duel atop the Tower of Hanoi. By then, the Tower's sixth and final ring had almost been completed. Varis drove Playmaker into a corner by creating an Extra Link, but Playmaker was able to endure and Extra Link his own monsters to Varis's. He defeated him, and as he had promised, Varis stopped the Tower of Hanoi and released the absorbed data harmlessly, causing the Tower to disintegrate. Varis logged out, vowing that he would continue to hunt the Ignis as long as they were a threat to humanity.
Despite appearing to disintegrate, the Tower remained in the ruins of LINK VRAINS and was forgotten after SOL Technolgies created LINK VRAINS 2.0. Varis and the Knights reactivated the Tower to search for Lightning with the help of Kolter, Emma, and Yusaku's coding skills, modifying it to create a powerful scan program that revealed Lightning had been hiding in Mirror LINK VRAINS.
- Yu-Gi-Oh! VRAINS episode 20: "A Piece of the Puzzle"
- Yu-Gi-Oh! VRAINS episode 30: "Under VRAINS"
- Yu-Gi-Oh! VRAINS episode 31: "Showdown in the Sewers"
- Yu-Gi-Oh! VRAINS episode 32: "The Tower of Hanoi"
- Yu-Gi-Oh! VRAINS episode 42: "Storm Access"
- Yu-Gi-Oh! VRAINS episode 43: "The Reveal"
- Yu-Gi-Oh! VRAINS episode 84: "Payback"
- Yu-Gi-Oh! VRAINS episode 34: "Roots of Evil"
- Yu-Gi-Oh! VRAINS episode 35: "The Hollow"
- Yu-Gi-Oh! VRAINS episode 36: "A Bridge Too Far"
- Yu-Gi-Oh! VRAINS episode 37: "Out on a Limb"
- Yu-Gi-Oh! VRAINS episode 38: "Looking Back"
- Yu-Gi-Oh! VRAINS episode 39: "Ring the Bell"
- Yu-Gi-Oh! VRAINS episode 40: "Gore at War"
- Yu-Gi-Oh! VRAINS episode 41: "Truth and Consequences"
- Yu-Gi-Oh! VRAINS episode 45: "Standing Tall"
- Yu-Gi-Oh! VRAINS episode 46: "Link to the Future"