At this point, one could only rely on absorbing materials to upgrade skills. However, upgrading a skill to an Ancestral God skill required Ancestral God-level materials.
Ancestral God-level materials were exceedingly rare in the universe, originating from Ancestral God-level Exotic Beasts, Spiritual Plants, or other non-intelligent lifeforms. The upper limit for such lifeforms was the Ancestral God level. Every non-intelligent lifeform capable of evolving into an Ancestral God was entirely unique and could form a race of its own.
For a non-intelligent lifeform to evolve into an Ancestral God was already incredibly difficult—far more so than for intelligent life. This resulted in Ancestral God-level Exotic Beasts and Spiritual Plants being extremely scarce and hard to find. Not to mention the monumental challenge of finding suitable upgrade materials from an already limited pool.
