Frostbitten Fingers

You fire a ray of intense cold that instantly induces frostbite. With a successful ranged spell attack, this spell causes one of the target’s hands to lose sensation. When the spell is cast, the target must make a successful Dexterity saving throw to maintain its grip on any object with the affected hand. The saving throw must be repeated every time the target tries to manipulate, wield, or pick up an item with the affected hand. Additionally, the target has disadvantage on Dexterity checks or Strength checks that require the use of both hands. After every 10 minutes of being affected by frostbitten fingers, the target must make a successful Constitution saving throw, or take 1d6 cold damage and lose one of the fingers on the affected hand, beginning with the pinkie.