Affinity relies heavily on nonbasic lands like Spirebluff Canal, Fiery Islet, Steam Vents, and Urza's Saga, so an additional Blood Moon turns all of those into Mountains and can functionally strand them off blue mana, leaving only their two basic Islands and Mox Opal (which is not a land and is unaffected) to cast blue spells. Damping Sphere taxes each additional spell they cast per turn, which punishes their tendency to chain multiple cheap artifacts, and it also makes any single land that is tapped for two or more mana produce only colorless mana instead. The Legend of Roku is too slow against their low curve and proactive artifact synergy plan. Thraben Charm's creature-damage mode is fine but replaceable since Galvanic Discharge and Goblin Bombardment already answer their small creatures like Pinnacle Emissary tokens.