Arcane Batteries

Arcane batteries have been used for centuries to create long-term magical effects. It has been well understood that the latent magic present in enchanted items can serve as a basic mana supply for long-term spells. When set up this way, the caster does not need to keep focus, nor supply any additional mana. These batteries can last for days, years, or indefinitely, depending upon the spell and strength of the enchanted item. The method for creating these batteries is a closely guarded secret, with only the most capable mages learning the secrets behind them.