A focus is an object that assists in using magic and casting spells, typically used by mages who are less skilled or powerful in order to shore up their weaknesses. A focus may or may not have any inherent power in and of itself.

Runes can be considered a highly codified form of focus. Others include utilizing an object such as a wand or staff to assist in channeling mana, making gestures with the hands or a wand to better control the direction and formation of a spell, chanting words to help the caster maintain focus on what they're doing, and so forth.

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