Elephant Grass

Black creatures are locked out of attacking you entirely, no questions asked; everyone else has to commit two mana per attacker just to declare combat against you, which makes alpha strikes financially absurd in the early game. That tax compounds against go-wide aggression precisely when the aggressor can least afford it, buying the defending player the first several turns of the game more or less for free. The design here is a study in deliberate impermanence: cumulative upkeep is the meter running, and the age counters that steadily drain the controller's tempo make the enchantment self-limiting. By the time you have paid the upkeep four or five times, the enchantment costs more than it stops, and you let it die. So this is a card built to do one job (stall the opening) and then politely retire, rather than a permanent fixture. The age-counter clock is the balancing discipline; without it, a green enchantment that broadly forbids combat damage at the cost of a single mana would be oppressive in any deck that simply wanted to durdle toward a payoff. With it, Elephant Grass is a finite, front-loaded purchase: enormous value in the first few upkeeps, a liability by the late game, and a clean expression of how cumulative upkeep was meant to price a powerful effect by the turn rather than by the spell.