Badlands

Both a Swamp and a Mountain in its rules identity, taps for either color with no life paid and no condition to satisfy, available the turn it lands: this is the structural argument that has shaped two-color mana for thirty years, one of the Alpha duals that set the baseline. Every dual-land cycle printed since defines itself against it. Shocklands ask two life and a tap-status choice. Fetchlands solve them by going and getting them. Painlands charge per use. Filter lands route through other mana. Triomes add a third color and arrive tapped. The Rakdos slot specifically has been revisited as Blood Crypt, Blackcleave Cliffs, Graven Cairns, Sulfurous Springs, Blightstep Pathway, and Haunted Ridge, each one a different attempt to approximate what Badlands does for free. The land-type subtypes matter mechanically too: any card that fetches a Swamp or a Mountain finds this, which is why the unconditional duals remain the load-bearing piece in formats that allow them. Its Reserved List placement halted reprints in 1995 and turned the cycle into the most durable scarcity asset in the game, but the design point is older and more interesting than the price tag: this is what an unconditional two-color land looks like, and the entire history of mana fixing since has been Wizards working out what to charge for it.