The Wanton Imp
Casting time: 1 reaction, which you take when you see a creature within 60 feet of you casting a spell
Range: 60 feet
You attempt to interrupt a creature in the process of casting a spell. Make an ability check using your spell casting ability. The DC equals 12 + the spell’s level. On a success, the creature’s spell fails and has no effect.
As a bonus action, this spell can also be used to break spell concentration. Casting this spell as a Bonus action forces a Concentration check verses your spell DC. On a failed check the concentration spell ends.