Tezzeret's Gatebreaker

The enters-trigger does the honest work: dig five deep, keep a blue or artifact card, bottom the rest at random. That's colorless selection filtered toward exactly the cards an artifact-and-blue shell wants to see, a smoothing effect the deck buys without spending colored mana up front. The real cost shows up later, and it's steep: the unblockable activation asks for five generic, a blue pip, the tap, and the artifact itself off the battlefield. That sequencing is the design's whole logic. Four mana for a single filtered card is a modest rate on its own; the payoff is that the artifact stays on the battlefield as a stored end-game switch, ready to flip a clogged ground into lethal once you've assembled a team worth swinging. The front half hands you selection and then sits quietly; the back half converts a stalled board into a one-turn kill on a turn of your choosing, a different rhythm than a combat trick or evasion aura held for the exact kill step. The namesake telegraphs the intended home: an artifacts-and-blue archetype that wants both the early digging and a late-game way to push damage through. The construction hedges against dead draws through the enters-trigger itself, not the sacrifice cost: if the alpha strike never materializes, you already cashed the card in the moment it resolved. What's left is a value-first piece wearing a finisher's clothing, which is why that enters-trigger has to justify the slot by itself.