At that point, a medium world can double the innate potential of its world guardians. So a creature with a potential of 80 units will have a Power Core of 160 units after they become a world guardian.
As if that isn't bad enough, the medium world can also raise the talent of its world guardians all the way to the limit of 100 units. So their Power Core can reach 200 units.
The extra power that the world grants the world guardians is why the world guardians can wield forces of nature. In the case of the storm god, the extra power from the world is why it can control storms in this world.
When a small world becomes a medium world, the medium world will cut down on the number of world guardians it can have so that it can double the power of its world guardians. So the mark of a medium world is the shift from prioritizing quantity to prioritizing quality.
