Underworld Spirit Beads

It was said that where the world of life met the world of death, something called underworld spirit rock could form. The underworld spirit beads were refined from that rock.
This kind of thing was extremely, extremely rare in the current world. It was basically impossible to find one. Only sects with extremely ancient inheritances could have managed to preserve a few.
It was said that the life and death energy within the underworld spirit beads could allow a Life Star expert to grow infinitely closer to breaking through to the Netherpassage realm. In the current world, it was a treasure that no money could buy.