Chief of the Foundry: This is a great construct type that buffs every other thing in this deck except for the Herald of Anguish. Very relevant and great value.
Foundry Inspector: Again, a great construct type that reduces the cost of every other thing in the deck except for the Herald. Might consider subbing this out for something better (suggestions welcome!).
Herald of Anguish: At the moment I only own one of these cards so that is all that is in here. Super relevant because of the [Improvise] mechanic. I can often get this on the board turn 4 or 5 causing it to start discarding your opponent's hand! Might include a second if/when I get another. Also a great flying block.
Metallic Mimic: This card plus the Ballista is our bread and butter. Dropping the Mimic and naming "Constructs" causes almost everything in the deck to come down with an additional +1/+1 on it. Huge and dirty combo with the Ballista as it immediately gives you an additional 1 damage 'ping' to any target. I have won many games on this filthy combo alone.
Noxious Gearhulk: Good top-end card that is relevant due to the Artifact and Construct card types. Gets buffed by everything and the creature destroy and life gain is a nice bonus. Not necessarily an 'auto-include' but it does a good job filling the top-end. Suggestions welcome for this as well.
Scrap Trawler: Again, very relevant Construct creature type. Big combos can be had here with all of the other artifact creatures in the deck. 2 of them is nice but I found any more was unnecessary. Feel free to sub this out with a suggestion!
Scrapheap Scrounger: Amazing value in this card. It can easily become a 4/3 or even 5/4 and comes back either on its own, or through the Trawler. Also good for crewing our Heart of Kirans.
Traxos, Scourge of Kroog: I have not found a deck that is more applicable to this card than this deck. 90% of the deck is going to untap this thing and it just keeps swinging in for huge damage. Super cheap to bring out too this is a definite 2 of, if not 3 (although is Legendary...).
Walking Ballista: The star of the deck. This thing puts in work and will not quit. Can get huge with the Foundry Chief and the Mimic and dishes out instantaneous damage whenever and wherever you need it. Definite 4-of.