One of the Translator's Rings, made by a transmutation specialist who found a number of ways to convert one type of magical energy into another.

Constructed by bending a tuning fork into a ring and placing that on a rowan tree to be grown into the wood (which is then excised to retrieve the ring), this ring allows the wearer to use their reaction to hold out their palm and absorb incoming thunder or force damage into the Wave Converter.  They become immune to the absorbed damage type until the start of their next turn.  Note the damage total and the number of dice rolled for the absorbed damage.  While the ring is "charged" this way it gives off a faint ringing hum audible in a 20 foot radius.  On their next turn the wearer can apply the stored energy to a damage roll.  If they do not, they take half the absorbed damage (rounded down) as it spills out of the ring.

If they roll damage on their turn and are applying that damage to a single target, the wearer can apply a number of dice equal to the number of dice of absorbed damage of the other type of damage than the one absorbed (if the Wave Converter absorbed force damage, it deals thunder damage, and vice versa) they can apply that damage to a the damage roll.  What dice are rolled depends on the attack made.

The Wave Converter adds d12s to an unarmed strike or natural weapon attack, d10s to melee weapon attacks, d8s to ranged weapon attacks and melee spell damage rolls, and d6s to ranged spell damage rolls.  If a damage roll fits more than one of these categories (such as applying one of the smite spells to an attack) the wielder can choose which they wish to apply the extra damage to.

If the wearer rolls a damage roll that applies to more than one creature at once, they can apply one extra die of that damage roll's die to a number of targets up to the number of damage dice absorbed.  The extra die's damage is of thunder if the Wave Converter absorbed force damage or of force damage if the Wave Converter absorbed thunder damage.

The Translator's Rings do not function if more than one such ring is worn on a given hand, as such a character can effectively wear a number of the Translator's Rings equal to the number of hands they have.