Dampen

You shoot a powerful jet of water at a creature of your choice within range. You make a ranged spell attack against the target and deal 1d6 bludgeoning damage on a hit. The target then becomes drenched in magical water, and the first time the target takes cold or lightning damage until the end of your next turn they take an additional 1d6 of that damage. 

Any creature that is immune or resistant to cold or lightening damage is immune to the vulnerability caused by this spell.

This spells damage, and the additional damage you deal, increases by 1d6 when you reach 5th level (2d6), 11th level (3d6), and 17th level (4d6).