Ancient Den

Portable Hole

When Portable Hole enters, exile target nonland permanent an opponent controls with mana value 2 or less until Portable Hole leaves the battlefield.

Ensoul Artifact

Enchant artifact
Enchanted artifact is a creature with base power and toughness 5/5 in addition to its other types.

Darksteel Citadel

Frogmite

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

Memnite

Dispatch

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

Cranial Plating

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

Stonecoil Serpent

Reach, trample, protection from multicolored
Stonecoil Serpent enters with X +1/+1 counters on it.

Steel Overseer

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

Arcbound Ravager

Sacrifice an artifact: Put a +1/+1 counter on Arcbound Ravager.
Modular 1 (This creature enters with a +1/+1 counter on it. When it dies, you may put its +1/+1 counters on target artifact creature.)

Vault of Whispers

Ornithopter

Disciple of the Vault

Whenever an artifact is put into a graveyard from the battlefield, you may have target opponent lose 1 life.

Blinkmoth Nexus

{T}: Add {C}.
{1}: Blinkmoth Nexus becomes a 1/1 Blinkmoth artifact creature with flying until end of turn. It's still a land.
{1}, {T}: Target Blinkmoth creature gets +1/+1 until end of turn.

Seat of the Synod

Mishra's Bauble

{T}, Sacrifice Mishra's Bauble: Look at the top card of target player's library. Draw a card at the beginning of the next turn's upkeep.