Foil

The free counterspell with a price tag written in cards instead of mana. The alternative cost asks for a specific tax: an Island and one other card off the top of your hand, which is why this favors blue decks running plenty of Islands. That construction is the whole design. The hard cost is steep enough that nobody runs Foil to play it fair; the appeal is the tempo of holding up a counter while tapped out, paying for it from a resource your opponent cannot see or attack. Force of Will pioneered the free-counter shape (life plus a blue card), and Foil is the mono-color cousin that swaps the life payment for two discards and a color restriction. The card math is the cost: you spend three cards (Foil plus the Island plus one more) to deny a single spell, a three-for-one trade that only makes sense when the spell you are countering would do more damage resolving than three cards' worth, or when stopping it this turn outweighs the card economy you will miss later. That arithmetic is what keeps it honest. It rewards decks that flood the hand and can afford to bleed deep at a critical juncture, and punishes the impulse to fire it off at anything that resolves. A free counter is always tempting; Foil's discipline is that it forces you to decide whether this is the spell worth three cards to stop.