Rusted Relic

The metalcraft gamble distilled into a single permanent: pay four mana for an inert artifact that becomes a 5/5 only while you hold a sufficient artifact count together. The condition counts itself, so it is really asking you to commit to two more artifacts before this one earns its slot, and the moment that third permanent leaves (a Disenchant, a chump-traded Equipment, a sacrificed token), the Golem reverts to a defenseless object that cannot block or attack. That conditional animation is the whole tension. A vanilla 5/5 for four would be a finished card; this one trades guaranteed stats for a discount that only pays out inside a shell already built to flood the field with cheap artifacts. It rewards the same builds that want Galvanic Blast or Mox Opal turned on, and punishes the metalcraft mirror where both players are racing to strip each other's count below three. The design lesson it carries is that metalcraft as a keyword always cuts both ways: the artifact you are counting can itself be the artifact that gets removed, and a creature whose existence depends on a number you do not fully control is a creature your opponent gets to interact with twice, once at the body and once at the condition.