Myr Enforcer

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

Hovermyr

Etherium Sculptor

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

Apostle's Blessing

({W/P} can be paid with either {W} or 2 life.)
Target artifact or creature you control gains protection from artifacts or from the color of your choice until end of turn.

Chromatic Star

{1}, {T}, Sacrifice Chromatic Star: Add one mana of any color.
When Chromatic Star is put into a graveyard from the battlefield, draw a card.

Myr Servitor

At the beginning of your upkeep, if Myr Servitor is on the battlefield, each player returns all cards named Myr Servitor from their graveyard to the battlefield.

Ichor Wellspring

When Ichor Wellspring enters or is put into a graveyard from the battlefield, draw a card.

Seat of the Synod

Great Furnace

Vault of Whispers

Darksteel Citadel

Stoic Rebuttal

Metalcraft — This spell costs {1} less to cast if you control three or more artifacts.
Counter target spell.

Galvanic Blast

Galvanic Blast deals 2 damage to any target.
Metalcraft — Galvanic Blast deals 4 damage instead if you control three or more artifacts.

Frogmite

Tree of Tales

Ancient Den

Ardent Recruit

Metalcraft — Ardent Recruit gets +2/+2 as long as you control three or more artifacts.

Thoughtcast

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

Defiant Salvager

Sacrifice an artifact or creature: Put a +1/+1 counter on Defiant Salvager. Activate only as a sorcery.