Capítulo 1727: No Vandalism Allowed.

Those are just limited uses of the Authority of the void universe. A world god will be able to do more with it. They will be able to reduce the resistance of the void universe against their Supreme Law and Will, so the amount of power they will be able to wield will be much higher. 

This is mostly what Legion knows about the use of Authority, but it is more than enough for them to be concerned and invested in its acquisition. They have tried to create it on their own through their Divine Spark clone, but Legion-9 failed to create it. By their estimate, they will either need to fully comprehend the Supreme Law of Order or have Legion-9 evolve to become a world forge. 

They haven't achieved either of that in the 10,000 years that they have been trying. It is not because they have been lazying around. It is because 10,000 is too short to achieve either of them and because they don't plan to comprehend the Supreme Law of Order anymore.