Malcator, Purity Overseer

The threshold is the whole gambit here: a 1/1 legendary body that immediately hands you a 3/3 Golem, then promises another 3/3 every end step you can push three artifacts onto the battlefield. That "under your control this turn" clause is doing careful counting work, and it counts entries, not casts, which quietly widens the on-ramp: token generators, artifact clones, treasures, clues, food, and free artifact creatures all tick the meter without a spellcast in sight. The Golem it makes on arrival is not incidental to that math; it is the first free step, so any turn you deploy Malcator you are already one-third of the way to the payoff. The design tension sits in the fragility of the enabler. A 1/1 that needs to survive to your end step, and needs a board built to spew artifacts, asks you to sequence a whole turn around a creature that dies to any incidental damage. Get the engine humming and it churns out a 3/3 a turn for free; leave it stranded on an empty board and it is a 1/1 that gave you one Golem. The three-artifact bar is the governor: it keeps the recurring token honest by demanding a deck actually committed to flooding the battlefield with artifacts rather than one that merely happens to run a few. It rewards the artifact-density build and offers nothing to the deck that only splashes the color.