Carpet of Flowers
The purest hate card Wizards ever printed against a single color, and the only one whose payoff scales directly off the opponent's land count. Most color-hosers from the early era hit creatures or punished a player for tapping the wrong color; this one watches an opponent's Islands accumulate and converts each into a mana of any color you like, once per turn, with no card cost beyond the green it took to deploy it. The design logic is asymmetric ramp: against a deck stacking Islands to fuel counterspells and card draw, you gain a mana advantage that grows in lockstep with their own engine, and because the mana comes in any one color you choose, it fixes as well as it accelerates. The catch is total dependence on the opponent: against any deck not playing Islands, it produces nothing and sits as a one-mana enchantment doing literally zero work. That conditionality is the design's entire premise. It is built to be the answer you reach for when blue is dominant and dead weight when it is not. The timing rewards reading the turn, too: the trigger fires at the start of each main phase, not at instant speed, but the "if you haven't added mana with this ability this turn" clause is a "may," so you can decline it precombat and bank the acceleration for your postcombat plays instead, choosing which main phase the mana lands in.
