Snow-Covered Swamp

The reason this exists is the snow supertype, and the reason snow matters is that it gave designers a way to draw a meaningful line through your manabase without touching the mana it produces. A black source that taps for black, indistinguishable in function from its ordinary counterpart, but carrying a single hidden bit of information: this land is snow. That bit is what every snow payoff reads. The original Ice Age cycle made snow-covered basics a deckbuilding cost, a deliberate friction against splashing, since you had to commit slots to lands that did nothing extra on their own. The modern revival inverted the logic: instead of taxing you for running them, cards reward you, so the snow basic becomes free upside in any deck whose payoffs care, with no cost beyond agreeing to play the snow version of a land you were running anyway. That is the elegant part of the design. The land's mana ability is untouched, so it never compromises consistency; the supertype rides along silently until something looks for it. It is one of the cleanest examples of a card whose entire identity lives in a supertype on the type line rather than in any printed effect, a switch that stays off until the rest of the deck flips it on.