Etched Champion

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

Ethersworn Sphinx

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)
Flying
Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card with lesser mana value. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)

Darksteel Citadel

Counterspell

Etherium Spinner

Whenever you cast a spell with mana value 4 or greater, create a 1/1 colorless Thopter artifact creature token with flying.

Myr Enforcer

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

Ornithopter of Paradise

Sojourner's Companion

Affinity for artifacts
Artifact landcycling {2} ({2}, Discard this card: Search your library for an artifact land card, reveal it, put it into your hand, then shuffle.)

Island

Ornithopter

Plains

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.

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.)

Barbed Spike

When Barbed Spike enters, create a 1/1 colorless Thopter artifact creature token with flying, then attach Barbed Spike to it.
Equipped creature gets +1/+0.
Equip {2}

Dispatch

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