Cranial Plating

Equipped creature gets +1/+0 for each artifact you control.
{B}{B}: Attach Cranial Plating to target creature you control.
Equip {1}

Frogmite

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

Etched Champion

Metalcraft — Etched Champion has protection from each color as long as you control three or more artifacts.

Seat of the Synod

Signal Pest

Battle cry (Whenever this creature attacks, each other attacking creature gets +1/+0 until end of turn.)
Signal Pest can't be blocked except by creatures with flying or reach.

Baleful Strix

Flying, deathtouch
When Baleful Strix enters, draw a card.

Myr Enforcer

Steel Overseer

{T}: Put a +1/+1 counter on each artifact creature you control.

Dispatch

Tap target creature.
Metalcraft — If you control three or more artifacts, exile that creature.

Tolarian Academy

{T}: Add {U} for each artifact you control.

Slate of Ancestry

{4}, {T}, Discard your hand: Draw a card for each creature you control.

Bident of Thassa

Whenever a creature you control deals combat damage to a player, you may draw a card.
{1}{U}, {T}: Creatures your opponents control attack this turn if able.

Vault Skirge

({B/P} can be paid with either {B} or 2 life.)
Flying
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Welding Jar

Sacrifice Welding Jar: Regenerate target artifact.

Master of Etherium

Master of Etherium's power and toughness are each equal to the number of artifacts you control.
Other artifact creatures you control get +1/+1.

Thoughtcast

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

Ornithopter

Vault of Whispers

Glimmervoid

At the beginning of the end step, if you control no artifacts, sacrifice Glimmervoid.
{T}: Add one mana of any color.