Mind Stone

The original solution to a problem ramp artifacts have always carried: the dead draw in the late game. Mana rocks accelerate you into your spells and then sit on the table as topdecks you no longer want, a tax that scales inversely with how much you needed the acceleration in the first place. The sacrifice clause closes that loop. Tap for colorless while you are building toward something, then cash the rock in for a card once the curve has crested. The genius is that the second mode costs mana too, so it cannot be a free cantrip you cycle on turn one; it asks you to commit the rock as a rock first and only later convert it, which keeps the artifact honest as acceleration rather than card advantage on demand. That template (a colorless mana source with a built-in conversion to a card) has been recut many times since, and the design language around "ramp that does not strand you" traces cleanly back to this two-mana body. The colorless-only output is the cost of the flexibility: it fixes nothing, but the cards built in its image rarely do, because the draw clause is the part doing the real work.