Sunstone

Damage prevention you pay for in land drops. The original snow mechanic from Ice Age tied a handful of effects to a deliberately scarce resource: snow-covered lands, which you chose to run over basics that produced the same mana without the downside of being a sacrifice target. This artifact turns that resource into a repeatable Fog, but the activation cost is what makes the exchange unusual. You pay to assemble it, pay mana again every time you want the effect, and each use eats a snow land off the battlefield for good. So the prevention is repeatable on paper and self-limiting in practice: every activation shrinks the mana you have to power the rest of your game, until the device that stops combat has cannibalized the board that lets you cast anything else. A one-shot Fog is a card you spend and forget; this is a permanent that converts standing mana into damage prevention, a slower trade that asks whether stopping one alpha strike is worth thinning your own resources to do it. It belongs to an early era of design experiment, when Wizards was still testing whether a parallel land subtype could carry its own balancing levers, with the sacrifice clause acting as the brake. The snow theme then lay largely dormant for years before later sets revived it with a cleaner execution.