Mirrodin Besieged

Metalcraft — Ardent Recruit gets +2/+2 as long as you control three or more artifacts.

({T}: Add {G}.)

Return up to two target creature cards from your graveyard to your hand.

Target creature gets +2/+2 until end of turn. Metalcraft — That creature gets +4/+4 until end of turn instead if you control three or more artifacts.

Flying Whenever you cast an artifact spell, you may untap target creature.

Counter target spell, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Target creature gets +1/+1 and gains trample until end of turn.

When Oculus dies, you may draw a card.

Creatures your opponents control get -2/-0 until end of turn.

Trample

Battle cry (Whenever this creature attacks, each other attacking creature gets +1/+0 until end of turn.) Kuldotha Ringleader attacks each combat if...

Sacrifice an artifact: Gnathosaur gains trample until end of turn.

Burn the Impure deals 3 damage to target creature. If that creature has infect, Burn the Impure deals 3 damage to that creature's controller.

When Blisterstick Shaman enters the battlefield, it deals 1 damage to any target.

When Phyrexian Rager enters the battlefield, you draw a card and you lose 1 life.

When Caustic Hound dies, each player loses 4 life.

As an additional cost to cast this spell, sacrifice a creature. Draw three cards.

Defender Metalcraft — As long as you control three or more artifacts, Spire Serpent gets +2/+2 and can attack as though it didn't have defender.

Put target artifact, creature, or enchantment on top of its owner's library.

Training Drone can't attack or block unless it's equipped.

{2}{G}: Regenerate Tangle Hulk.

{R}: Target creature can't block Spin Engine this turn.

Sacrifice an artifact: Regenerate Rusted Slasher.

Metalcraft — Razorfield Rhino gets +2/+2 as long as you control three or more artifacts.