It wasn't rare to see things that were 10000 meters long, but most of them were dead or plants. Living creatures that were 10000 meters long were very rare.
There were some in the void, but they only existed in the void and rarely appeared in the real world.
An ordinary world could not bear such a life form, and a slight carelessness would lead to the destruction of the plane barrier.
For a living being to reach such a size, it meant that it had already surpassed the limits of ordinary life and had entered a different life form.
This form was the creator.
If the Masters of creation wanted to, they could grow to a hundred thousand meters or even a million meters.
Of course, this required a huge amount of energy to support it. Otherwise, even a creator-level expert wouldn't be able to maintain this form for a long time.