One Month

Aleron's soul, looking at him but sitting in a meditative cross-legged position in his sea of consciousness, was surrounded by whirling soul energy he was absorbing.

Using that pure soul essence from this mysterious area, he refined his soul. This process was simple but painful and slow, depending on multiple factors.

Upon reaching Unbound-rank, one's soul is already complete. It had fully formed.

To make it more powerful, people must break their limits and make it more powerful via Soul Refining.

In simple terms, it was the same as when a blacksmith heats the iron and then smashes it. Of course, the result would be different between this blacksmith process and Soul Refining.