Shawn's transformation was actually nearing its final step.
Because of the experience from previous enlightenment, Shawn continually reshaped his understanding of his innermost self. During this process, he discovered that the restrictions of Spiritual Spells were in fact imposed on him by the Extraordinary Essence, being creations forced to adapt to the Twisted Law of the world.
"In other words, the Mind Energy I'm using now still originates from Su'en's Brain."
"Now."
"What I need to do is to completely transform the power of Su'en's Brain into my own power!"
Using the operational law of the Arcanist Path to reverse-engineer the Wizard Path.
One law understood, all laws understood!
Essentially, both the Mind Path and Wizard Path are about utilizing supernatural energy, and different methods of utilization create different professional paths.
"I'm using the Spiritual Ability Law of the Alien Monster Empire now!"
"So?"
