Iron Suitcase

The cheapest artifact you can run purely as a scry engine, and one built to keep earning its slot after the enters-the-battlefield trigger has resolved. Most one-mana artifacts that dig do so once and then sit as inert board clutter; this one holds a second job in reserve, converting itself into a 3/3 flier whenever the mana is idle. That two-part structure (immediate library-smoothing on entry, a repeatable late-game threat baked into the same permanent) is what separates it from the disposable card-selection rocks it otherwise resembles. The scry 2 is the reason it enters a deck; the activated body is the reason it doesn't rot into a dead draw twenty turns deep in a grind. Because the animation lasts only through the turn you pay for it, the flying beater works as a pressure valve rather than a permanent clock: swing when you want the damage, and it reverts to a static artifact by cleanup, sliding back under the sorcery-speed removal that would happily eat a stationary creature. The flexibility of timing carries more of the design than the raw rate does. It is a smoothing tool that refuses to be a spent shell, and a mana sink that never demanded a slot on its own merits, folded into a single cheap permanent.