Upgrading medicine in Phantom Blade Zero enhances the percentage of HP, damage negation, and Sha-Chi that healing items restore, providing significant benefits to players.
Players can upgrade their medicine once they reach the Green Serpent House, located in the west of Pangzhen. This area is accessible during the second chapter of Pangzhen's storyline. Specifically, it becomes available after defeating Xie Qiudong, The Divine Healer, and progressing further into the town. The Green Serpent House is identifiable by its prominent green banners and the distinct bell.
At the Green Serpent House, an Apprentice Healer can upgrade your medicine. The upgrade materials required are Apprentice Healer's Memories and Skilled Healer's Memories, which players may have already collected during their exploration of the game world. Upon the player's first visit to the Green Serpent House, they will also receive the Green Serpent Brew, a medicine designed to remove status effects.