As for the Orbital Dominion, it has to do with how he can use these celestial bodies in combat. It turns out he can use them for both attacking and defending.
This tome taught him how to create shields around his planets and how to orbit and align them in a way that makes incoming attacks easy to defend against.
It is all technical, and even though Kent doesn't have access to the seven tomes left, he knew there was a buildup to the Orbital Dominion. He knew it involved the laws, so he chose to create something and experiment first.
The Stellar Cataclysm is basically the combat aspect of the entire Soul Universe. Kent now possesses abilities like Solar Flare, which allows him to harness the power of the sun and shoot it like a laser.
Abilities like Nova Burst, where he can temporarily transform a summoned star into a nova, releasing an explosive burst of energy that can knock back and severely damage all enemies within a large radius.
