Mirrodin Besieged

When Ichor Wellspring enters the battlefield or is put into a graveyard from the battlefield, draw a card.

Destroy target creature with flying. Its controller gets a poison counter.

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

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.

Trample

{2}{B}: Dross Ripper gets +1/+1 until end of turn.

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

Destroy target creature, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already the...

When Myr Sire dies, create a 1/1 colorless Myr artifact creature token.

Return up to two target nonland permanents to their owners' hands.

When Viridian Emissary dies, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle your library.

Create two 1/1 colorless Myr artifact creature tokens.

Flying Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)

Flying When Serum Raker dies, each player discards a card.

Flying When Serum Raker dies, each player discards a card.

Put any number of target artifact cards from your graveyard on top of your library. Draw a card.

Destroy target artifact. You gain life equal to its converted mana cost.

Attacking creatures get +1/+0 and gain first strike until end of turn.

{U}: Gust-Skimmer gains flying until end of turn.

{W}: Bladed Sentinel gains vigilance until end of turn.

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

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.