Crimestopper Sprite [Murders at Karlov Manor]

As an additional cost to cast this spell, you may collect evidence 6. (Exile cards with total mana value 6 or greater from your graveyard.)

Flying

When Crimestopper Sprite enters the battlefield, tap target creature. If evidence was collected, put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)