Dragonfly Suit

Flying
Crew 1 (Tap any number of creatures you control with total power 1 or more: This Vehicle becomes an artifact creature until end of turn.)

Thoughtcast

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

Ardent Recruit

Metalcraft - This creature gets +2/+2 as long as you control three or more artifacts.

Malcator's Watcher

Flying, vigilance
When this creature dies, draw a card.

Etherium Sculptor

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

Goggles of Night

Whenever equipped creature deals combat damage to a player, scry 1, then draw a card. (To scry 1, look at the top card of your library, then you may put that card on the bottom.)
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Ancient Den

Plains

Myr Enforcer

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

Lens Flare

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)
Lens Flare deals 5 damage to target attacking or blocking creature.

Spire Serpent

Defender
Metalcraft - As long as you control three or more artifacts, this creature gets +2/+2 and can attack as though it didn't have defender.

Chromatic Star

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

Lumengrid Drake

Flying
Metalcraft — When this creature enters, if you control three or more artifacts, return target creature to its owner's hand.

Auriok Sunchaser

Metalcraft — As long as you control three or more artifacts, this creature gets +2/+2 and has flying.

Island

Court Homunculus

This creature gets +1/+1 as long as you control another artifact.

Darksteel Citadel

Rusted Relic

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