Sky Diamond

The blue member of the mono-colored Diamond cycle, the line of two-mana artifacts that each tap for a single color and enter tapped. The cycle is the direct descendant of the Moxen, stripped of everything that made the Moxen broken: where Mox Sapphire was free and produced blue the moment it resolved, this costs two and forfeits its first activation. That tapped-on-entry clause is the entire balancing mechanism. It means the Diamond never accelerates you while it is fresh; the ramp shows up a turn later, which converts a two-mana rock into a two-turn investment rather than a one-turn explosion. The design is deliberately conservative, and it became the template Wizards returns to whenever it wants colored ramp that cannot enable a first-turn combo: the same enters-tapped friction reappears in later artifact-acceleration cycles when the goal is fixing and ramp without speed. The deeper lesson is about where flexibility gets paid for. A fixed mana rock lets any deck reach into blue without playing Islands, and that reach has to cost something; here the price is charged in tempo rather than in mana value. You pay for the freedom to ignore your color requirements by waiting a turn for the payoff, which is exactly why this design has aged into a safe one.