Aggressive Counter

You attempt to interrupt a creature in the process of casting a spell. Once the spell is successfully countered with this spell the person casting the original spell takes 1d4 psychic damage for each level of the spell they were trying to cast. This damage can not be mitigated by any means and bypasses resistance and immunity becomes resistance as their own magics backfire upon them. If the creature is casting a spell of 5rd level or lower, its spell fails and has no effect. If it is casting a spell of 6th level or higher, make an ability check using your spellcasting ability. The DC equals 10 + the spell's level. On a success, the creature's spell fails and has no effect.

At Higher Levels. When you cast this spell using a spell slot of 6th level or higher, the interrupted spell has no effect if its level is less than or equal to the level of the spell slot you used.