Creeping Cold

This spell turns a target’s sweat and moisture to ice, creating blisters as the ice forms on its skin. Unless succeeding at a Constitution saving throw, a single creature that you can see within range takes 1d6 cumulative points of cold damage per round (i.e. 1d6 hitpoints of damage on the 1st round, 2d6 the 2nd and 3d6 the 3rd). Only one save is permitted against the spell, and is made at the time of casting. The damage is taken at the end of the caster's turn each round. 

At higher levels. Cast as a 4th level spell extends the creeping cold by 1 round: in the 4th round, the target loses an additional 4d6 hitpoints.