Balloon

One creature that you can see within range must roll a constitution saving throw or be effected by this spell for the duration. The affected targets speed is halved and it takes a -2 penalty to AC and Dexterity saving throws. 

The creature affected by this spell makes another constitution saving throw at the end of each of its turns. On a successful save, the spell ends. When this spell ends, the target pops and takes 1D12 thunder damage for every failed saving throw it made against this spell.