Cloudpost

The mana it produces scales not with how many lands you control but with how many copies of itself (and its later kin) are in play, which inverts the usual ramp math: the first Cloudpost is a tapped land that makes one colorless, while the fourth makes four, and the curve bends upward as fast as you can draw and play them. That quadratic ceiling is what eventually made the Locus subtype a banned-and-restricted concern across multiple formats. The companion that pushed it over the line was Glimmerpost, whose lifegain bought the time the deck needed, and Vesuva, which could copy a Cloudpost to double-count itself. Built around that engine, the archetype known as Cloudpost or 12-Post aimed to skip several turns of ramp and slam a payoff well ahead of schedule. The land enters tapped and produces only colorless, the two restrictions doing the balancing work: you cannot tap it for mana the turn you play it, and you must build a deck that wants generic mana on the back end. Those costs read as small until you notice they are the only brakes on an effect that otherwise compounds with every land drop. It is the rare ramp piece whose power lives entirely in its own redundancy, a land that is mediocre alone and oppressive in fours.