From Guild of Archivists

Lifestone is a rare mineral of unknown properties found in the southern hills of Serenia. The root system of the Memory Chamber plant, a flowering fungus, must be in contact with a lifestone in order to perform its function of removing and storing memories. This suggests that the lifestone serves the plant as an essential nutrient. If contact with a lifestone is broken, the Memory Chamber gradually loses its memory-storage ability. Ultimately the plant will die.

The Protectors of Serenia normally keep the lifestone on a pedestal in a ceremonial Root Chamber. However, in case of need, the lifestone may be placed in direct contact with the roots in the heart of the Memory Chamber.