Affinity for artifacts reduces a spell's cost by one generic mana for each artifact its controller has on the battlefield. It only lowers generic mana, so colored requirements such as Thoughtcast's blue mana still have to be paid. The keyword debuted in the set Mirrodin, where cheap artifact lands let spells like Frogmite and Myr Enforcer be cast for free within the first few turns. The Modern format helped put Arcbound Ravager into the spotlight as one of the auto-includes for any "Affinity" deck.