This armor has a metal cylinder attached at the nape of the neck, and several tendrils reaching from the canister to the armor’s reinforced pauldrons. As a reaction to taking acid, cold, fire, lightning, or thunder damage, you may activate the armor and gain one charge. While the armor is activated you have resistance to the damage type of the attack until the end of your next turn and gain one additional charge each time you are hit by this damage type for the duration.
As an action you may expend up to 10 charges to force all other creatures within a 10-foot radius to make a Dexterity saving throw, as pure elemental energy is discharged from small holes in the pauldrons. This saving throw has a DC equal to 10 + your proficiency. Each creature takes 1d6 Force damage per charge expended on a failed save, or half as much on a successful one. All unexpended charges are harmlessly vented from the canister each day at dawn.