Mystical Dispute

The engineering feat is hiding a tax inside a targeting condition. Blue has always had cheap ways to tax the stack: Spell Pierce narrows by card type, Mana Leak stays symmetrical in its cost, Daze fronts a card. This one keys its discount to a color rather than a type, so its efficiency rises with an opponent's commitment to blue. Aimed at a red or green spell it is a full-price soft counter, asking three mana to slip past; aimed at a blue spell it does the same taxing work for a single mana. The effect never changes (counter unless the controller pays three); only the price of asking the question moves. Against a blue opponent that price collapses, so casting your key spell into open mana becomes a live gamble all game, because the answer sits in their hand at almost no cost. That is the sharp part of the design: the more an opponent leans on the very color this spell hunts, the more efficiently it hunts them, without the counter itself ever getting harder to pay through. The template (a spell that costs less when it targets a specific color) has since appeared on other colors and card types, but the counterspell version reads cleanest, because the decks most likely to draw the discount are the exact decks trading spell for spell on the stack in the first place.