Razorfield Rhino

Six mana for a 4/4 is a body nothing would run on rate alone, and that is exactly the trade being offered: a payoff that only pays when the rest of your board has cooperated. Reach three artifacts and the Rhino swings as a 6/6, a fine common-rarity beater; fall short and it sits there as a colorless creature costing as much as far better things. The Metalcraft condition is a static state check rather than a triggered ability, so the size adjusts in real time as artifacts enter and leave the battlefield. That has a subtle consequence in combat: a removal spell aimed at one of your other artifacts can shrink the Rhino mid-attack without ever targeting it, dropping a 6/6 attacker back to 4/4 before damage. The fragility is the price of the upside, and it asks nothing clever of its pilot beyond holding three or more artifacts on the board. Metalcraft is the structural idea at work, a colorless reward sized so the bonus reads as a genuine incentive to flood the board with cheap artifacts, equipment, and tokens rather than a default you can ignore. As an artifact creature itself the Rhino counts toward its own threshold, but only as one of the three required, which keeps the condition honest: it can never single-handedly switch itself on.