Tarnished Citadel

City of Brass priced its fixing in damage you take whenever you tap it, a steady drip that adds up across a long game. This land reverses the structure: tapping for colorless is free, and the 3-damage cost is reserved for the moments you actually need a colored mana you can't get elsewhere. That changes the math entirely. Instead of paying a point every turn the land does its job, you pay a lump sum only on the turns the painless mode falls short, which means a deck with enough other sources can run it as a near-free fixer that bites only in emergencies. The 3 damage is a real number, not the 1 of a typical painland, so the land punishes overreliance hard: lean on the colored ability across several turns and it will drain a large chunk of your life total on its own. The design is built around restraint. It rewards a manabase where the colorless mode covers most of your needs and the painful color mode is the exception, not the plan. Played that way, it is some of the cleanest fixing a colorless-hungry deck can ask for; played as a primary color source, it is a self-inflicted clock.