Siege Mastodon

Whispersilk Cloak

Equipped creature can't be blocked and has shroud. (It can't be the target of spells or abilities.)
Equip {2}

Rally the Forces

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

Gold Myr

Viridian Claw

Equipped creature gets +1/+0 and has first strike.
Equip {1}

Accorder Paladin

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

Victory's Herald

Flying
Whenever this creature attacks, attacking creatures gain flying and lifelink until end of turn.

Origin Spellbomb

{1}, {T}, Sacrifice this artifact: Create a 1/1 colorless Myr artifact creature token.
When this artifact is put into a graveyard from the battlefield, you may pay {W}. If you do, draw a card.

Leonin Skyhunter

Memnite

Iron Myr

Ardent Recruit

Metalcraft - This creature gets +2/+2 as long as you control three or more artifacts.

Concussive Bolt

Concussive Bolt deals 4 damage to target player or planeswalker.
Metalcraft — If you control three or more artifacts, creatures controlled by that player or by that planeswalker's controller can't block this turn.

Leonin Relic-Warder

When this creature enters, you may exile target artifact or enchantment.
When this creature leaves the battlefield, return the exiled card to the battlefield under its owner's control.

Kuldotha Ringleader

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

Razorfield Rhino

Metalcraft — This creature gets +2/+2 as long as you control three or more artifacts.

Silvercoat Lion

Signal Pest

Battle cry (Whenever this creature attacks, each other attacking creature gets +1/+0 until end of turn.)
This creature can't be blocked except by creatures with flying or reach.

Peace Strider

When this creature enters, you gain 3 life.

Myrsmith

Whenever you cast an artifact spell, you may pay {1}. If you do, create a 1/1 colorless Myr artifact creature token.

Plains

Arrest

Enchant creature
Enchanted creature can't attack or block, and its activated abilities can't be activated.

Galvanic Blast

Galvanic Blast deals 2 damage to any target.
Metalcraft — Galvanic Blast deals 4 damage instead if you control three or more artifacts.

Master's Call

Create two 1/1 colorless Myr artifact creature tokens.

Mountain

White Sun's Zenith

Create X 2/2 white Cat creature tokens. Shuffle White Sun's Zenith into its owner's library.