Noon-Midnight Stone

A strange stone material that turns to a supreme yang attribute during the zi (midnight) and wu (noon) hours, causing mutual感应 (induction/sensing) between pieces. This感应 only works effectively in places with extremely heavy yin energy like the Netherworld River Land. In ordinary environments, even powerful cultivators cannot detect their感应. It is extremely rare, not produced on the Tianyuan Continent and scarce on other continents. It has very few uses for cultivators.