Crystallized Demon Core

A demon core from a high-level demon beast that has been left for an extremely long time, causing it to completely crystallize. It becomes indistinguishable from ordinary spirit crystals even to powerful divine sense. It is useless for alchemy as it contains a deadly poison, but it is the best material for refining flying needle-type magic treasures. Needles made from it are extremely fast, nearly invisible when flying, and ideal for sneak attacks.