Myr Enforcer

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

Mountain

Rusted Relic

Metalcraft — Rusted Relic is a 5/5 Golem artifact creature as long as you control three or more artifacts.

Stern Lesson

Draw two cards, then discard a card. Create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")

Powerstone Shard

{T}: Add {C} for each artifact you control named Powerstone Shard.

Lembas

When Lembas enters, scry 1, then draw a card.
{2}, {T}, Sacrifice Lembas: You gain 3 life.
When Lembas is put into a graveyard from the battlefield, its owner shuffles it into their library.

Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Draw a card.

Stone Retrieval Unit

When Stone Retrieval Unit enters, create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")

Island

Excavation Explosion

Excavation Explosion deals 3 damage to any target. Create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")

Thoughtcast

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

Alchemist's Vial

When Alchemist's Vial enters, draw a card.
{1}, {T}, Sacrifice Alchemist's Vial: Target creature can't attack or block this turn.

Galvanic Blast

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