Memnite

Tempered Steel

Artifact creatures you control get +2/+2.

Etched Champion

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

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.)

Steel Overseer

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

Dread Statuary

{T}: Add {C}.
{4}: Dread Statuary becomes a 4/2 Golem artifact creature until end of turn. It's still a land.

Cranial Plating

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

Dispatch

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

Ornithopter

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Plains

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.

Dismember

({B/P} can be paid with either {B} or 2 life.)
Target creature gets -5/-5 until end of turn.

Indomitable Archangel

Flying
Metalcraft — Artifacts you control have shroud as long as you control three or more artifacts. (An artifact with shroud can't be the target of spells or abilities.)

Ethersworn Canonist

Each player who has cast a nonartifact spell this turn can't cast additional nonartifact spells.

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.