Ring of Devouring – This ring possesses an intense appetite. Once per day, the user can attune the ring to fire, ice, electricity, or acid, and the ring can consume that type of material. Effectively, this grants damage reduction to the chosen type, but only towards physical manifestations of the damage (i.e. actual acid via a spell, but not from a corrosive weapon).
Image Source: BK Items by Gloroh on DeviantArt – https://bit.ly/2SvA5Qu