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

Canon

A Scroll is a magic item. It is a physical storage device for a single spell, which can be used only by a caster. Casters may create a scroll or scrolls on their turn, for a significantly higher cost in juice than simply casting the same spell.

Speculation

A scroll with a spell of the same Discipline as the Caster has a greater effect than one cast by a different Discipline.^Erf-b1-p006

Even a caster who is normally not proficient at casting spells beyond his own discipline can use scrolls of other disciplines with some effectiveness.

It is not clear whether casting a spell from a scroll spends any of the caster's juice.