Active Counterspell

You attempt to interrupt a creature in the process of casting a spell. Make a spell attack roll against the caster's spell save DC. On a success, 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 of 3 or lower, the slot isn’t expended.

Each level upcast adds another level of spell slot whose spell slot cannot be recovered by the original caster. Until 6th level where that spell slot can be siphoned and collected as a part of the reaction used to counter it.