"Numeron" was a term that could be said to run through all of Yu-Gi-Oh! ZEXAL. It was the core around which the fourth generation's main story unfolded.
Legend had it that at the end of time, where all things began, the world had originally been nothing but a void. There were no planets, no life, not even the concept of a universe. Meaningless "nothingness" occupied all time and space.
Until a card was born.
Yes, that was right. In the World of Yu-Gi-Oh!, the origin of all things could be a card, known as the Numeron Code. Just as its name implied, this card was the foundational code that constructed countless universes and dimensions of reality. Everything, every law in the universe, was born and operated based on this card's code.
Anyone who could control the Numeron Code would gain the power to rewrite reality at will. That person could alter the existing world according to their wishes, overwrite the established past, and create any future they desired. They would basically be a Creation God.
That was also why, when assessing the strength of Yu-Gi-Oh!'s bosses across the generations, Don Thousand from the fourth generation was always a strong contender.
Don Thousand's prototype came from Hindu creation mythology. After acquiring a portion of creation's power in the anime, Don Thousand used that power to create the card series known as Numeron.
Thus, to recreate the Numeron cards' creative attributes in the setting, the anime deliberately reflected the trait of "primordial power capable of rewriting the world" in the Deck's design. When the Numeron Deck appeared in the original anime, it truly left viewers stunned, with all sorts of absurd effects that broke convention. It even created the famous scene of "rewriting the opponent's Deck."
Still, perhaps only such a performance