Fen Hauler

A 5/5 with a printed seven-mana cost is a bluff: that number is only what you pay when the board is empty. Fill it with Servos, Thopters, and assorted trinkets first, and improvise lets you tap those artifacts after mana abilities to shave the cost down to a splash of black plus whatever junk is lying around. The unblockable-by-artifact-creatures clause points the same deck at the same target: the pile of small artifacts you flood the board with to make this cheap is the pile you want swinging in a metalcraft mirror, where the bodies most likely to gum up combat are precisely the artifact creatures this thing walks past. The discount comes from your own board; the evasion reads the opponent's; both reward the same artifact-dense strategy this closes out. That symmetry is the whole pitch, and it is also the ceiling. The body does nothing on its own, the evasion is conditional on what the opponent happens to control, and improvise only ever refunds cost; it never generates advantage. This is a common-rarity curve-topper for artifact aggro: a serviceable finisher once the board is already stocked, and dead weight anywhere that fuel does not exist.