Mana Leak

The original tax counter, and the template every "unless its controller pays X" spell printed since has had to reckon with. The design answers a different question than the hard counter does. Counterspell is unconditional: it stops anything, any turn, for the same two mana, and it never decays. The tax counter trades that certainty for a sliding window. The number itself is the whole design. Three is enough to be a true counter on turns one through four, when nobody has a spare three mana lying around, and a soft tax thereafter, when the game has opened up and the opponent can simply eat the cost. That sliding window is what makes the card feel like a clock on the opponent's progression: it is best the turn it represents the most pressure, and it decays into a speed bump exactly as the game state stops rewarding it. Wizards has spent decades dialing the tax up and down from this baseline. Daze charges a returned land instead of mana, Miscalculation taxes two, Logic Knot scales the tax to delve. None of those iterations changed what the original established: that a counterspell does not have to stop everything to be worth a card, it just has to stop the right thing at the right time, while it can still afford to.