Tidal Flats

A defensive enchantment built around a tax mechanic that almost nobody used for what it actually did. The repeatable ability looks like a fog-adjacent damage-prevention tool, but its real structure is a toll: a single double-blue activation reaches every non-flying attacker at once, and each one's controller must choose between paying a mana or handing first strike to your blockers. That framing inverts the usual blocker math. Normally the attacker dictates which trades happen; here the defender sets the terms, and a ground-pounding aggressor either drains mana across the whole board on the way in or runs its creatures into blockers that now strike first. The cost structure keeps it honest: the double-blue activation has to clear every turn, the per-creature tax scales with the width of the attack so a deep enough board can swallow the mana drain and come anyway, and the ability does nothing on its own without bodies to block behind. It dates from blue's early combat-altering experiments, before the color settled into bounce, counterspells, and card draw as its identity. The design space (a defensive engine that punishes attacking rather than preventing it) never really propagated; first strike granted at instant speed to blockers is a strange lever for blue to hold, and later sets gave the color cleaner tools for surviving aggression. What remains is a curiosity that asks the attacker to do arithmetic every turn and rarely got the chance to.