Errowain's Counterspell

You attempt to interrupt a creature in the process of casting a spell. The creature makes a Constitution saving throw (DC 3 plus your spellsave DC). The creature adds the level of their spell being cast to the result. On a failed save, the spell dissipates with no effect, and the action, Bonus Action, or Reaction used to cast it is wasted. If that spell was cast with a spell slot, the slot isn't expended.

Using a Higher-Level Spell Slot. You add 1 to the DC of the Constitution saving throw for each spell slot level above 3.