Steelclad Serpent

The drawback here is doing almost no work, which is the whole problem with the card. A 4/5 body for six mana asks you to keep one other artifact on board just to swing, and in any deck that wants to run a vanilla blue beater this large, that condition is trivially met or trivially ignored. The serpent still blocks at full size regardless; the restriction only ever bites in the rare board state where you control no other artifact, exactly when you would not want to attack anyway. This is the kind of artifact-creature filler an artifact-themed block produces by the dozen: a body stapled to a flavor-justified clause that reads like a cost but functions like a footnote. Blue rarely wants a clunky ground creature at this rate, and the artifact synergy implied by the type line and the attack condition never resolves into a payoff the card itself provides. What it offers is an artifact type attached to a workable defensive statline, which is to say it is a creature you might run when you need an artifact that also happens to be a wall, not the other way around.