"Legendary Number", pluralized as "Legendary Numbers" in the Japanese version, are "Number" cards which are unique located in Number's Ruins across the world, protected by guardians. They play an major part of the Legendary Number War arc of Yu-Gi-Oh! ZEXAL. So far, each one of these cards has been based on figures from history, as the canon portrays it.
"Legendary Numbers" are part of original 100 "Number" cards, but unique. Each of these "Numbers" correspond to a legend inscribed on the walls of the ruins, telling the story of the person who occupied that location in a previous era, before they became ruins due to the ravages of time. Mach, for example, was a Pegasus who served a legendary hero, Durbe. Three knights who lived in his land attempted to usurp the King, but were intercepted by Mach and his master. Since the hero was unwilling to kill his former comrades, both master and steed were eventually defeated and killed. However, the hero's fellow knights regretted their actions and they buried him and Mach together. Mach later became the "Legendary Number" spirit guardian of "Number 44: Sky Pegasus".
In Yu-Gi-Oh! ZEXAL, the "Legendary Numbers" are unique Numbers whose cards were used by Astral eons ago to seal Don Thousand in the Barian World's Sea of Ill Intent. If Astral obtains them all, he would discover the location of the Numeron Code. However, if the Barian deity Don Thousand obtains them all, he would be fully revived.
There is a connection between the "Legendary Numbers" and the Seven Barian Emperors, which was revealed when Astral absorbed "Numbers" "44" and "54". He saw Durbe's past life as a knight owning a Pegasus and Alit's past life as a gladiator. Don Thousand hinted at Vector's past life as a mad prince. When Astral questioned Jinlong if the person he was talking about was Mizael, the latter confirmed this. However, Mizael, even with Jinlong revealing Mizael's past life as a dragon tamer, refused to believe he was once a human. Afterwards, Roku found a statue of a military commander named Kiraku Souhachi at the Duel Lodge, which bore great resemblance to the Barian Emperor Gilag, with Ponta confirming that Kiraku Souhachi was, indeed, Gilag's past life as a military commander.
When Vector released Don Thousand, Thousand revealed that in order to fully revive him, Vector must collect these seven "Legendary Number" cards. Later, Vector convinced Mizael and Durbe to take part in this endeavor, with the assistance of Mr. Heartland, who is now an insect. Also, Yuma Tsukumo and Astral resolved to take the "Legendary Numbers" after receiving a message from the former's father.
After that, Alit acquired the third "Legendary Number", "Number 54: Lion Heart" from Number 54's guardian, but gave it to Nistro so he could control him. After they lost the Tag Duel, Nistro gave Yuma the "Number".
Returning to Heartland City, Yuma discovered by television that yet another "Number" was found, this time inside the Duel Lodge, and rushed to take it. Gilag went to the same ruins, but Ponta took his body over and challenged Yuma to a Duel for "Number 64: Sandayu the Veteraccoon" and Gilag's body. Yuma won and obtained the "Number".
When the Different Dimension Airship crashed at sea, Rio was called to the bottom of the sea by the guardian Abyss. Following her along with Yuma and Astral, Shark eventually defeated Abyss' Number 73: Abyss Splash the Roaring Waterfall Deity after being shown memories from his past life, using the ruins' second "Legendary Number", Number 94: Crystal Zero the Polar Ice Princess, putting all the "Legendary Numbers" into someone's possession.
Yuma and Astral eventually gain the Second Legendary Number back from Number 96 at the cost of Astral sacrificing himself to protect Yuma from a fatal attack.
|#||Monster||Sealed Form||Number location||Guardian||Legendary Figures||Owner(s)|
|Sky Pegasus||Right shoulder plate||Mach||Durbe||Yuma/Astral|
|Ethereal Dragon - Draggluong||Right wing||Jinlong||Mizael||Kite Tenjo|
|Lion Heart||Left side of chest||Number 54's guardian||Alit|| Alit (Formerly)|
|Sandayu the Veteraccoon||Frontpiece of helmet||Ponta||Gilag||Yuma/Astral|
|Judge Buster the Adjudicutting Djinn||Right side of chest||Battle Ox||Vector|| Number 96 (Formerly)|
|Abyss Splash the Roaring Waterfall Deity||Right thigh plate||Abyss||Unknown||Rio Kastle (Formerly) Reginald Kastle|
|Crystal Zero the Polar Ice Princess||Left side of dress||Abyss||Unknown||Reginald Kastle|