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.

Frogmite

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

Springleaf Drum

{T}, Tap an untapped creature you control: Add one mana of any color.

Memnite

Fabricate

Search your library for an artifact card, reveal it, put it into your hand, then shuffle.

Ornithopter

Nadu, Winged Wisdom

Flying
Creatures you control have "Whenever this creature becomes the target of a spell or ability, reveal the top card of your library. If it's a land card, put it onto the battlefield. Otherwise, put it into your hand. This ability triggers only twice each turn."

Unsummon

Return target creature to its owner's hand.

Darksteel Citadel

Collective Resistance

Escalate {G} (Pay this cost for each mode chosen beyond the first.)
Choose one or more —
• Destroy target artifact.
• Destroy target enchantment.
• Target creature gains hexproof and indestructible until end of turn.

Thought Monitor

Affinity for artifacts
Flying
When Thought Monitor enters the battlefield, draw two cards.

Treasure Vault

{T}: Add {C}.
{X}{X}, {T}, Sacrifice Treasure Vault: Create X Treasure tokens.

Waterlogged Grove

{T}, Pay 1 life: Add {G} or {U}.
{1}, {T}, Sacrifice Waterlogged Grove: Draw a card.

Breeding Pool

({T}: Add {G} or {U}.)
As Breeding Pool enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped.

Forest

Summoner's Pact

Search your library for a green creature card, reveal it, put it into your hand, then shuffle.
At the beginning of your next upkeep, pay {2}{G}{G}. If you don't, you lose the game.

Kappa Cannoneer

Improvise (Your artifacts can help cast this spell. Each artifact you tap after you're done activating mana abilities pays for {1}.)
Ward {4}
Whenever Kappa Cannoneer or another artifact enters the battlefield under your control, put a +1/+1 counter on Kappa Cannoneer and it can't be blocked this turn.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Mana Leak

Counter target spell unless its controller pays {3}.

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Tanglepool Bridge

Tanglepool Bridge enters the battlefield tapped.
Indestructible
{T}: Add {G} or {U}.

Island

Pick Your Poison

Choose one —
• Each opponent sacrifices an artifact.
• Each opponent sacrifices an enchantment.
• Each opponent sacrifices a creature with flying.