Expose Weakness 2014

Select one creature you can see within range, and one damage type that isn’t bludgeoning, piercing, or slashing. The target must make a Charisma saving throw or lose any resistance to that damage type for the duration. The first two times each round that the target takes damage of the chosen type, it takes 2d6 additional damage of that type.

When you cast this spell using a spell slot of 6th level or higher, the number of times each round the additional damage can occur increases by 1 for every two slot levels above 4th.