Patchwork Automaton

Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
Whenever you cast an artifact spell, put a +1/+1 counter on this creature.

Arcbound Crusher

Trample
Whenever another artifact enters, put a +1/+1 counter on this creature.
Modular 1 (This creature enters with a +1/+1 counter on it. When it dies, you may put its +1/+1 counters on target artifact creature.)

Flux Channeler

Whenever you cast a noncreature spell, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Surge Conductor

Whenever another nontoken artifact you control enters, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Cloud Key

As this artifact enters, choose artifact, creature, enchantment, instant, or sorcery.
Spells you cast of the chosen type cost {1} less to cast.

Evolution Witness

{1}{G}: Adapt 2. (If this creature has no +1/+1 counters on it, put two +1/+1 counters on it.)
Whenever one or more +1/+1 counters are put on this creature, return target permanent card from your graveyard to your hand.

Falco Spara, Pactweaver

Flying, trample
Falco Spara enters with a shield counter on it.
You may look at the top card of your library any time.
You may cast spells from the top of your library by removing a counter from a creature you control in addition to paying their other costs.