Defend the Hearth

The asymmetry is the entire point. Most fog effects stop all combat damage flat, sweeping the attacker's clock and the defender's blockers out of the exchange alike for a single turn of breathing room. This one narrows the window: damage to players is prevented, but creatures still trade, chump, and die in the dirt. For a defender, that means you can block freely, let the unblocked attackers swing into a wall of prevention, and watch the combats you chose to contest resolve exactly as they would have without the spell, only with your life total intact. The combat math does not change; what changes is the penalty for letting the rest of the team through. An evasive threat with no blocker still deals you nothing, since prevention covers every point of combat damage aimed at a player, blocked or not. The cost of that protection is its silence everywhere else: it answers nothing that does not come through the combat step, so noncombat burn, direct drain, and any source that bypasses attacking go untouched. This belongs to the green tradition of treating combat as a problem the attacker must solve twice, the lineage of effects that let you defend without conceding the board. A standard fog buys a turn and freezes the battlefield; this one keeps the bodies trading while sparing only the face damage you were never going to profit from taking.