Frost Marsh

A tapland that adds blue or black is an old bargain: pay a turn of tempo on entry, get two colors out of one slot, the same trade the original tapped duals and their gain-life descendants offered. What sets this one apart is the supertype riding along. It counts as a snow permanent, which means it feeds an engine that has nothing to do with fixing two colors at once. Cards that scale off the number of snow sources you control, or that ask for snow mana specifically, treat this as more than a Dimir tapland; it pays for effects that basic snow lands cannot cover when a deck needs an exact off-color source, since a basic snow land only produces one color. That is the real reason the pairing exists: snow payoffs push you to flood the manabase with snow sources, but a two-color snow deck still needs honest fixing, and stapling the snow supertype onto a dual surface lets the enabler count stay high without surrendering consistency. Entering tapped is the toll for stacking both jobs onto one land, and a deck leaning on the unhurried midgame that snow rewards tend to want is built to swallow that toll without much complaint.