Tarnation Vista

The second ability is the tell: it scales off your board's color diversity, but only counts colors among your monocolored permanents, which is a much sharper restriction than it first reads. A five-color pile of gold cards produces exactly one mana here, the chosen color, because none of those permanents contributes a color to the tally. The land wants a battlefield built the way a devotion deck is built, in single-pips: a mono-red creature, a mono-white enchantment, a mono-blue artifact, each one adding its color to the pool. Meet that condition across three or four colors and this becomes a ritual attached to a land, spitting out a rainbow of mana off a single tap. Fall short and it is a tapland with a filter attached, the baseline it can never dip below thanks to the color-of-choice ability that always works. That floor is what makes the design honest: it never bricks completely, so the payoff ability can be pushed hard without stranding you on a dead land in the openings when your board is empty. The entering-tapped clause and the extra generic on the big activation are the other levers holding the ceiling down. It is fixing that rewards a specific deckbuilding shape rather than raw greed, closer in spirit to the devotion payoffs than to a plain untapped dual.