Possibility

Each space had its own size, amount of energy, and resources that could grow in each space. These and some other factors determine the rank of a space, and the highest rank is Half-World.

If the space somehow managed to expand significantly or to increase its volume of energy by several times, then Half-World was transformed into something bigger, like a real World.

It was almost impossible to achieve this artificially, as it took too many resources to do so, so even if the owner of the space was someone on the Transcendence Stage, its maximum was Half-World.

For a space to become a real World, it required the efforts of millions of beings, all of whom had to be alive, going through their own difficulties and gaining achievements.

This made the world what it was supposed to be. The strongest worlds were obviously those of the Pillars, for they were the most numerous and powerful races. Compared to their worlds, the others seemed weak and inferior.