The Stormstone is a Key Item in Xenoblade Chronicles 2. It is received from Misimisi during Precious Yearnings by having him appraise a Strange Mineral from a prospecting point near the Old Plumbing Entrance in the Empire of Mor Ardain.
Upon appraisal, Misimisi responds with, "Yes yes yes..This mineral called Stormstone. Stormstone occasionally create mini tornado windy effect. Quite popular in hot springs of Mor Ardain. Sink stone in water and pleasant bubbles rise up from below!"