Storm Cloud: once per day, you can cast Call Lightning 4th level) using this ring. 

At Home in the Storm: any creature attuned to this ring gains +1 bonus to con score. If attuned creature is a tempest cleric, they also receive +1 to wisdom score. If they are a Storm Sorcerer, they receive a +1 bonus to charisma score. Only one of these last two bonuses apply. In case of multiclassing, it will always be the class the creature had first or has the most levels. If it’s an even score, choose one of the two options.

Notes: Bonus: Constitution Score, Cleric, Druid, or Sorcerer