Reckless Fireweaver- One of the two wincons. Without Panharmonicon its a worthless 15 cent card. With it we can start swinging for lethal around turn 5 with the right cards. (For instance you can have Panharmonicon and two Reckless Fireweavers out turn 4. Turn 5, Put down two Servo Schematics. 6 artifacts, 2 damage per artifact per Reckless Fireweaver, 24 damage.)
Mechinized Production- Our other wincon. Put this on anything. Panharmoicon boom so many ETB triggers. Servo Schematic so many servos. Prophetic Prism so much card draw. Combustible Gearhulk, mill yourself to death.
Cogworker's Puzzleknot
/Servo Schematic- Our means of servo production. Their secondary abilities past the initial ETB servo production are not extremely impactful on the game but do help slightly.
Glint-Nest Crane-A good early game blocker that helps us dig for our important artifacts. Synergies later with Panharmonicon.
Prophetic Prism-More dig. Helps fix mana issues as well. Synergies later with Panharmonicon.
Inventors' Fair- Let's you tutor either Panharmonicon, Combustible Gearhulk, or if you really need it Servo Schematic
Combustible Gearhulk- Amazing ETB effects that, with the correct mana combinations, can provide a late game threat.
Authority of the Consuls- Only reason this deck runs white. This card counters both Saheli Cat and vehicle decks. It also procs Panharmonicon. Put in sideboard when against counterspell decks.
Saheeli Rai- Mainly used for her -2 ability, Allows you to copy Panharmonicon for more ETB value or
Cogworker's Puzzleknot
/Servo Schematic for much needed servo production.
Apparently Saheeli Rai shot up in price when I wasn't looking so I personally wouldn't spend the money for her but she is defiantly really good for the deck.
Padeem, Consul of Innovation (Currently in Maybeboard)- When playing with my Mardu-Panharmonicon deck at FNM one of the biggest problems it faced was removal of key pieces in the combo, namely Reckless Fireweaver and Panharmonicon. Padeem and counter spells like Metallic Rebuke and Negate should lessen the impact of hate.