Arcane Battery

This arcane crystal-core device stores vast amounts of raw magical energy, glowing brighter with each charge it holds. Invented by archmages obsessed with arcane efficiency, the Arcane Battery is both a backup and a boon. 

The battery contains a maximum of 24 charges (dependent on Tier). While holding or wearing the battery (can be worn as a necklace), you can use an action to expend charges from it to restore an expended spell slot, depending on the battery’s tier.

Battery Tiers (d6/2 or DM's choice)

You may spend charges equal to twice the level of the spell slot to restore it.

If you do not have enough charges, the attempt fails and no charges are spent.

Recharging the Battery

As an action, you can sacrifice an unused spell slot to restore twice its level in charges to the battery, up to its 18-charge maximum. For example, sacrificing a 5th-level slot restores 10 charges.

The battery regains no charges on its own (with the exception of the Bespoke version, which regains 1 charge daily)—only through this method.

Overload Discharge

You can attempt to restore charges beyond the battery’s limit, when you do the battery will begin to give off bright light and will violently discharge after a short period (enough time to throw up to 30 ft.). Each creature within 10 feet of the detonation must make a DC 15 Dexterity saving throw, taking 5d6 force damage on a failed save, or half as much on a success.

Notes: Spellcaster