The Source Essence!
Why were these cultivators in the Foundation Establishment Realm, whether demons or humans, so shocked? Because this stuff was genuinely rare and extremely difficult to refine.
Whether it was human cultivators refining spiritual energy, demons focusing primarily on their innate divine abilities, Buddhist body-refining cultivators, or even demonic cultivators centering their practice on fusing all sorts of bizarre and eccentric uncanny entities, the Source Essence was useful to all of them.
Chapter 232