Cymbals of the Immortal Storm

A pair of small, bronze cymbals with a chain for wearing around the neck. The holder can cast the thunderwave spell at will, by clapping the cymbals as he would if he cast the spell. For each level above first one additional use is expended. The thundering sounds are accompanied by a high ringing. The cymbals have eight uses, when the last use is expelled the holder must roll a d20. On a twenty all uses are refilled, on a one they burst into purple, heatless flame and burn to ashes. On any other number all uses remain expended and the holder must complete a long rest to replenish them.