Gem of Breath Absorption

Wondrous item (any gemstone) very rare

This gem is immune to damage from the breath weapons of all dragons. When it is exposed to the breath weapon of any true dragon, instead of taking damage, it absorbs the energy of the dragon's breath and stores it for later use. (This in no way affects the damage that other creatures take from the breath weapon, even the gem's holder.) While the gem is charged in this way, you can use an action to call forth the breath contained within. The gem expends all of its power to unleash a breath weapon with the same size, shape, damage type, damage dice, and saving throw as the breath that it absorbed. Once used in this way, it cannot be charged again until the next dawn. The gem can hold only one charge at a time.

Chromatic dragons will sometimes gift these gems to their most prized followers as a token of power, and to help spread fear and carnage. The Draconic Order appears to have a number of these gems that they use during combat with the Cult of the Wyrm, though it is not clear if the Order knows how to create them, if they have a horde of them they safeguard, or if they are getting them from someplace else.

These gems can be seen worked into weapons and armor.

See the variants armor of breath absorption and weapon of breath absorption for details.