The Crimson Dragon is a giant winged Aztec dragon, with a glowing red body. It has five fingers, similar to humans, bird-like legs, a long tail and neck and gold-colored eyes. On the end of its tail is a shovel-like dagger.
Ten thousand years before the present day events, the mighty Crimson Dragon along with Ancient Fairy Dragon, Black Rose Dragon, Black-Winged Dragon, Red Dragon Archfiend and Stardust Dragon fought the Crimson Devil, Red Nova.
During the battle, the Legendary Signer came forward from the ashes of a volcano and absorbed the Crimson Dragon's vast and limitless power through Blazing Soul, and used it to defeat and seal the Crimson Devil.
5,000 years before present day events, the People of the Stars, called upon the Dragon Star for aid to save their lands from the Earthbound Immortals that threatened the peace of their civilization. The Dragon Star answered their call and came down from the heavens in the form of the Crimson Dragon.
The Crimson Dragon had fought the Earthbound Immortals, with the help of its Five Servants. However, instead of Black-Winged Dragon, Life Stream Dragon was present. The dragons managed to seal the Earthbound Immortals within the Nazca Lines, but Ancient Fairy Dragon was lost during the battle, as Earthbound Immortal Uru dragged the dragon with it when it was sealed.
In their later rematch, the Crimson Dragon appeared again. However, everyone was there to witness it and with the four Signers present at the Fortune Cup, its appearance was more defined than the last time. Each birthmark was clearly represented and the dragon's head also changed. During the Duel, the legendary Dragon God transported Yusei, Jack, Luna and Akiza into an alternate dimension and showed a disturbing vision in which Satellite was being destroyed by an unknown force and in its place, a Dark Mark which resembled the Spider appeared.
The Red Dragon God showed itself once again to the four Signers at Rex Goodwin's home. Goodwin then revealed to them a secret that concerned the Red Dragon. It was able to influence fate itself, which is what led to the events that brought the Signers together.
After the King of the Netherworld was finally revived and headed toward New Domino City, where the Condor Geoglyph was, the Dragon God appeared in the sky, and took the Signers, along with their companions, to where the ultimate fight would be held.
After Yusei defeated Goodwin in the Shadow Turbo Duel, the Crimson Dragon arrived, and used "Majestic Star Dragon" to gain physical form, and destroyed the King of the Netherworld by flying through it. It disappeared after that.
Pre-World Racing Grand Prix
The Dragon appeared toward the conclusion of the Duel between Leo and Luna against Lester. As Lester's "Meklord Emperor Skiel" attacked Leo and caused him to be blown off the riding lane, the Dragon shot a sphere from its claw that engulfed Leo, saving him from the wall. After this, it disappeared. The Three Pure Nobles were surprised at the Crimson Dragon saving Leo since they knew Leo wasn't a Signer.
World Racing Grand Prix
Towards the end of the Ritual Duel between the Familiar of Red Nova and Jack Atlas, Red Nova appeared, summoned by his servant wanting to take Jack. However, the Crimson Dragon appeared and protected Jack. Greiger and Max identified the dragon as the shrine's protector Quetzalcoatl. Jack used the ability Blazing Soul to capture Red Nova and transfer its power into a card, and created "Red Nova Dragon". After Jack defeated the Familiar, the temple came crumbling down around Jack, Yusei, Greiger and Max. However, the Crimson Dragon protected the four of them and flew away afterward.
In his Duel with Halldor, when Yusei Summoned "Majestic Star Dragon", Halldor looked at it through his Rune Eye and briefly saw the Crimson Dragon. Halldor realized that the "Majestic Star Dragon" was the incarnation of the Crimson Dragon itself.
After Yusei won the Duel, Halldor used his Rune Eye once again and when he looked at Yusei, he saw "Shooting Star Dragon" and the Crimson Dragon. Halldor realized that the "Aesirs" saw the Crimson Dragon and Team 5D's as allies rather than enemies.
When Z-one was defeated in his Duel against Yusei, the Divine Temple shut down and began to collapse. As Team 5D's (minus Yusei) and Sherry head to their Duel Runners, the floor broke apart beneath them and everyone started to fall. The Crimson Dragon appeared and saved everyone, and transported them to a nearby highway.
Team 5D's future
The Crimson Dragon made one final appearance at the end of Yusei and Jack's last Duel. With the Signers' mission complete, the Crimson Dragon reabsorbed all of its Marks since the Signers no longer required them.
Yu-Gi-Oh! 3D Bonds Beyond Time
The Crimson Dragon appeared during the film Yu-Gi-Oh! 3D Bonds Beyond Time, to transport Yusei through time to chase after Paradox who was in Europe, where Jaden Yuki was. At that moment, Jaden was being assaulted by Paradox with "Stardust Dragon", however the Crimson Dragon appeared just in time to protect Jaden from the attack, and brought Yusei along with it.
Later, it transported Yusei and Jaden to the past, to Yugi Muto's time, at the moment when Maximillion Pegasus and people, including Solomon Muto, were attacked and killed by Paradox with "Stardust Dragon", "Cyber End Dragon", and "Rainbow Dragon". The Crimson Dragon than grabbed Yugi and took all three of them back thirty minutes prior to the moment when Paradox arrived where they teamed up in order to Duel Paradox.
An alternate version of the Crimson Dragon briefly appears when Jack Atlas Synchro Summons "Tyrant Red Dragon Archfiend" using "Scarlight Red Dragon Archfiend" as Synchro Material, and Jack invokes the Crimson Dragon during the Summon chant.
The Crimson Dragon appears in the 5D's manga but plays a more malefic role. Here, the Crimson Dragon is known as the Ultimate God, that infects humans with dark miasma, and turns them into its loyal followers, seeking only destruction and power. Like the anime counterpart, the Ultimate God created dragons known as Duel Dragons. However, the Duel Dragons' purpose was to seal the Ultimate God, though they can be forced to serve the Ultimate God against their will.
As a deity, the Crimson Dragon is practically capable of doing nearly anything it wishes. It possesses the ability to freely create, control and manipulate fire, flame, and heat at will.
To keep itself safe, the Crimson Dragon shared five fractions of its immeasurable energies and entrusted each to five humans it chose (eventually six), sensing their good hearts. It also has the extremely difficult ability to influence certain events in people's lives; for example, it caused its five chosen Signers to meet and befriend one another, so that they could tap into the dragon's full strength and abilities to save the world from annihilation once again.
It also possesses the exceedingly difficult ability to travel through time itself and freely enter various timelines and alternate realities; an ability shown in Bonds Beyond Time. While not stated, the Crimson Dragon can also cause some minor alterations. Yugi was brought from a future where Paradox succeeded, but that chain of events was prevented; it's possible it replaced the Yugi that should have taken his place with the one who helped defeat Paradox.
- Yu-Gi-Oh! 5D's episode 113: "Burning, Seething Soul! Scar-Red Nova Dragon"
- Yu-Gi-Oh! 5D's episode 7: "The Facility, Part 2"
- Yu-Gi-Oh! 5D's episode 30: "Fight or Flight"
- Yu-Gi-Oh! 5D's episode 5: "A Blast From The Past, Part 2"
- Yu-Gi-Oh! 5D's episode 26: "The Fortune Cup Finale, Part 2"
- Yu-Gi-Oh! 5D's episode 42: "The Signs of Time"
- Yu-Gi-Oh! 5D's episode 62: "Signs of Doom, Part 1"
- Yu-Gi-Oh! 5D's episode 64: "Signs of Doom, Part 3"
- Yu-Gi-Oh! 5D's episode 78: "Dawn of the Duel Board, Part 2"
- Yu-Gi-Oh! 5D's episode 128: "Yusei's Last Stand"
- Yu-Gi-Oh! 5D's episode 130: "Bound to the Future, Bonds to Our Companions"
- Yu-Gi-Oh! 5D's episode 142: "A Life-or-Death Battle! Machine Imperial God Dragon Asterisk"
- Yu-Gi-Oh! 5D's episode 150: "Entrusted Feelings of My Father"
- Yu-Gi-Oh! 5D's episode 151: "Converging Wishes"
- Yu-Gi-Oh! 5D's episode 154: "Shining Forth to the Future"
- Yu-Gi-Oh! 3D Bonds Beyond Time
- Yu-Gi-Oh! ARC-V episode 97: "Making it Mine"
- Yu-Gi-Oh! ARC-V episode 122: "Show of Nature"