|Natural Magic, Caster, Caster link, Juice, Scroll, Magic Item, Spell, Grandiocosmic Strings, Channels, Nodes, Dictums|
Caster proficiency: Novice – Adept – Master
A Caster can only spend a limited amount of this energy to cast spells on one turn.Erf-b1-p090 Apparently the juice replenishes at the start of new turn. It is possible that sleep either temporarily increases the limit of the juice or helps replenish higher amount of juice.Erf-b1-p084
Scrolls are a way to "store" juice for later use as casting scrolls do not seem to spend Caster's own juice.Erf-b1-p125, Erf-b1-p129 Casters create scrolls on their turn, for a significantly higher cost in juice than simply casting the same spell.
It is possible there are other costs (e.g. money) associated with scrollmaking, as otherwise one might suspect Duty would require casters to spend all of their 'off-combat' turns creating scrolls rather than 'taking it easy'.