Metalwork Colossus

This spell costs {X} less to cast, where X is the total mana value of noncreature artifacts you control.
Sacrifice two artifacts: Return Metalwork Colossus from your graveyard to your hand.

Myr Superion

Spend only mana produced by creatures to cast this spell.

Myr Scrapling

Sacrifice Myr Scrapling: Put a +1/+1 counter on target creature.

Myr Retriever

When Myr Retriever dies, return another target artifact card from your graveyard to your hand.

Foundry Inspector

Artifact spells you cast cost {1} less to cast.

Palladium Myr

Alloy Myr

Myr Battlesphere

When Myr Battlesphere enters, create four 1/1 colorless Myr artifact creature tokens.
Whenever Myr Battlesphere attacks, you may tap X untapped Myr you control. If you do, Myr Battlesphere gets +X/+0 until end of turn and deals X damage to the player or planeswalker it's attacking.

Myr Enforcer

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)

Jhoira's Familiar

Flying
Historic spells you cast cost {1} less to cast. (Artifacts, legendaries, and Sagas are historic.)

Myr Galvanizer

Other Myr creatures you control get +1/+1.
{1}, {T}: Untap each other Myr you control.