Secret Passage

Enters-tapped duals are the concession you make for the fixing: you resent them on turn one and forget about them by turn four. This one buys back its slowness on the far side of the game. Once your land drops stop mattering and flooding out becomes the actual threat, it stops being a passive tapland and starts converting excess mana into a Clue, then a card, off nothing but its own tap and some idle lands. That is a resolution a manabase card almost never earns: most taplands do nothing after they have done their one job. The Investigate framing is doing the structural work, letting a land carry a repeatable draw outlet without the design bolting on a bespoke sacrifice clause or inventing a new keyword to justify it. What it answers is a specific grindy Dimir problem: what should the land you drew off the top do when you have already hit every drop you need? The usual answer is nothing. Here the answer is that it keeps drawing, slowly and at a steep six-mana rate, but reliably, turning the late-game topdeck you would have groaned at into fuel instead of a dead card.