Coral Atoll

The "karoo" lands, sometimes called bounce lands, start here: a small mono-colored cycle in Visions that asked you to pay tempo for fixed mana production. The bargain is brutal in its honesty. The land enters tapped, then taxes you a second time by returning an untapped Island to your hand, so committing it costs you a full turn of land development and a card-economy hiccup, all to produce one colorless and one blue going forward. The sacrifice clause is the structural lock that makes the rest legal: you must already control an untapped Island, which gates the land behind a specific board state rather than letting it slot into any deck that wants the mana, and it pins the card permanently to blue. That single-Island requirement is also why it never matured into the genuinely flexible dual-land template; the later Ravnica bounce lands (the ones that return any land, tap for two colors, and drop the conditional sacrifice rider) are the refined descendant of exactly this idea, the design Wizards arrived at once it decided the tempo cost alone was enough friction and the gating sacrifice was overkill. As mana, it measures how much tax early Magic was willing to attach to a land that does nothing but ramp you a turn later, and the bounce-land formula got cleaner every time the idea came back.