Legendary Numbers surrounding Numeron Code.
Legendary Numbers are sub-archetype of "Number" cards that are special located in the Seven Ruins on Earth protected by guardians. Each of these "Numbers" resemble to a legend carved on the walls of the ruins, telling the story of the individual who controlled that area in a prior time, before they became ruins due to the effects of period.
Thousands of years ago, Astral during his battle against Barian deity used the "Legendary Numbers" to seal Don Thousand in the Barian World's Sea of Ill Intent as prisoner. If Don Thousand obtains all of them he will fully revive himself.