Falchion, Designer of the Reunion (CMB-033 SR) [Crimson Moon's Battleground]

[Enter] Look at the top seven cards of your deck and put them back in any order. Whenever your opponent plays a spell >>> Reveal the top card of your deck. Cancel that spell if its total cost is equal to the total cost of the card revealed this way. Put the card revealed this way on the bottom of your deck. This ability triggers only once per turn.