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Magic 101
Natural Magic, Caster, Caster link, Juice, Scroll, Magic Item, Spell, Grandiocosmic Strings, Nodes

Proposed Canon

"Juice" is a term describing the mental energy that a Caster uses to cast Spells.^{Erf-b1-p104, Erf-b1-p125, Erf-b1-p129}

A Caster can only spend a limited amount of this energy to cast spells on one turn.^Erf-b1-p090 Juice replenishes to full at the start of new turn. It is possible that sleep aids a Caster in performing actual spells.^Erf-b1-p084

Scrolls

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.