Chromatic Sphere

The cantrip-fixer that taught Affinity and every artifact-storm deck how to count to zero without bleeding cards. The trick is the replacement: spend a mana, get a mana of any color back, and the card doesn't thin your hand, it just exchanges generic for colored while drawing a fresh card on top. That makes it nearly free in spell-count terms, which is exactly what matters to combo decks that need a high density of cheap permanents and a smooth draw. The colorless mana floor (it costs one to play, one to activate, and returns one) keeps it honest as fixing: it is not ramp, it is laundering, converting bad mana into good without net acceleration. What it does net is an artifact entering and leaving the battlefield, a card replaced, and a death trigger if you want one. That bundle of incidental triggers is why it outlived its job as plain fixing: the same line that smooths a five-color deck's colors also feeds metalcraft counts, storm counts, and sacrifice synergies, all from a one-mana rock that asks nothing of your deck except that it survive long enough to be cracked. It is the rare fixer whose value scales not with how scarce your colors are but with how many things care that an artifact existed for a moment.