Snap-Flutter Slicer

Flash, flying
Whenever Snap-Flutter Slicer deals combat damage to a player you may exile that many cards face-down from the top of target player's library. You may look at and put any number of cards exiled by Snap-Flutter Slicer into its owner's graveyard for as long as they remained exiled, if you do, counter target spell with the converted mana cost equal to the the total converted mana cost of those cards.