The soul had four levels.
Mortal soul, Unfathomable soul, Abstract soul, and Paradisical soul.
The willpower had seven levels.
Theoretically, a mortal soul could give birth to a Level One willpower; however, it was much more common for a creature to nurture an unfathomable soul and then develop a Level One willpower.
With each subsequent level reached by one's willpower, there is a direct effect on the soul, which sees the unfathomable soul slowly evolve into an abstract soul.
The process of forging a Level Three Willpower augmented the unfathomable soul. By the time one's willpower was on the cusp of the Fourth Level, their soul would be ready to evolve into an abstract soul.
Although one's willpower and soul could evolve naturally with the passage of time, there was the Supreme Realm to assist the otherworldly creature in tempering their willpower, along with countless other kinds of cosmic treasures.
