Keystone

The keystone (kaname-ishi) is the node binding the primordial spirit Amon to the World Tree. In the world's electrical metaphor it is the 'substation' between the power plant (Amon) and the power line (the World Tree). Its bearer is a living sacrifice: first the priestess Silfaria, and then the princess Mari was to become one.

Feril's early reincarnation broke Silfaria's seal, which made Feril herself a potential new keystone-sacrifice.

Varis proposed a plan of 'distributed auxiliary keystones' (bunsan hojo kaname-ishi keikaku): twelve small stones forming a microgrid, each bound to an element for everyday needs. This spreads the load, removes the need for a single sacrifice, and brings abundance.