Galvanic Key

Untapping an artifact means nothing until the artifact is worth doing twice. On its own this is filler: pay three and tap to free up a single permanent, an expensive way to reuse a tap ability. The job it was built for is the artifact-side untap enabler, the cog that turns a one-shot activation into a repeatable one. Any artifact with a ability worth paying three mana per cycle to retrigger becomes a candidate, and a mana rock that taps for three or more crosses from break-even into profit. Flash is what saves it from being a clumsy main-phase chain: the untap can sit on the table as a held response, ready to re-arm a blocker's tap effect or steal an extra activation on an opponent's end step instead of being locked to your own turn. This is the workshop-bin component, the cheap part whose ceiling is entirely a function of what else is on the board. Read by its text it does almost nothing; read as part of a machine it is the piece that closes the loop.