Venomous Jeer

As a reaction to any attack or spell used against you, regardless of being dealt damage or suffering any negative effects, you may tell a loathsome joke about the one who made it. The target must make a Constitution saving throw, taking 2d6 poison damage on a failure or half as much on a success. If they fail their save, they become poisoned for 1 minute. While poisoned this way, the target only receives half the benefits of magical healing. 

At Higher Levels. When casting this spell with a spell slot of 2nd or higher level, increase the damage dealt by 1d6 for each slot level above 1st.