Mirrodin Besieged

As Mirrodin Besieged enters the battlefield, choose Mirran or Phyrexian.
• Mirran — Whenever you cast an artifact spell, create a 1/1 colorless Myr artifact creature token.
• Phyrexian — At the beginning of your end step, draw a card, then discard a card. Then if there are fifteen or more artifact cards in your graveyard, target opponent loses the game.

Myr Kinsmith

When Myr Kinsmith enters the battlefield, you may search your library for a Myr card, reveal it, put it into your hand, then shuffle.

Lodestone Myr

Trample
Tap an untapped artifact you control: Lodestone Myr gets +1/+1 until end of turn.

Gold Myr

Myr Scrapling

Sacrifice Myr Scrapling: Put a +1/+1 counter on target creature.

Myrsmith

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

Myr Landshaper

{T}: Target land becomes an artifact in addition to its other types until end of turn.

Urtet, Remnant of Memnarch

Whenever you cast a Myr spell, create a 1/1 colorless Myr artifact creature token.
At the beginning of combat on your turn, untap each Myr you control.
{W}{U}{B}{R}{G}, {T}: Put three +1/+1 counters on each Myr you control. Activate only during your turn.

Myr Mindservant

Hovermyr

Coretapper

{T}: Put a charge counter on target artifact.
Sacrifice Coretapper: Put two charge counters on target artifact.

Myr Matrix

Indestructible (Effects that say "destroy" don't destroy this artifact.)
Myr creatures get +1/+1.
{5}: Create a 1/1 colorless Myr artifact creature token.

Myr Sire

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

Darksteel Myr

Indestructible (Damage and effects that say "destroy" don't destroy this creature. If its toughness is 0 or less, it's still put into its owner's graveyard.)

Myr Battlesphere

When Myr Battlesphere enters the battlefield, create four 1/1 colorless Myr artifact creature tokens.
Whenever Myr Battlesphere attacks, you may tap X untapped Myr you control. If you do, Myr Battlesphere gets +X/+0 until end of turn and deals X damage to the player or planeswalker it's attacking.

Myr Welder

Imprint — {T}: Exile target artifact card from a graveyard.
Myr Welder has all activated abilities of all cards exiled with it.

Myr Superion

Spend only mana produced by creatures to cast this spell.

Suntouched Myr

Sunburst (This enters the battlefield with a +1/+1 counter on it for each color of mana spent to cast it.)

Brudiclad, Telchor Engineer

Creature tokens you control have haste.
At the beginning of combat on your turn, create a 2/1 blue Phyrexian Myr artifact creature token. Then you may choose a token you control. If you do, each other token you control becomes a copy of that token.

Myr Quadropod

{3}: Switch Myr Quadropod's power and toughness until end of turn.

Myr Prototype

At the beginning of your upkeep, put a +1/+1 counter on Myr Prototype.
Myr Prototype can't attack or block unless you pay {1} for each +1/+1 counter on it.

Myr Propagator

{3}, {T}: Create a token that's a copy of Myr Propagator.

Knighted Myr

{2}{W}: Adapt 1. (If this creature has no +1/+1 counters on it, put a +1/+1 counter on it.)
Whenever one or more +1/+1 counters are put on Knighted Myr, it gains double strike until end of turn.

Myr Retriever

When Myr Retriever dies, return another target artifact card from your graveyard to your hand.

Alpha Myr

Master's Call

Create two 1/1 colorless Myr artifact creature tokens.

Myr Galvanizer

Other Myr creatures you control get +1/+1.
{1}, {T}: Untap each other Myr you control.

Parcel Myr

Myr Enforcer

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

Myr Reservoir

{T}: Add {C}{C}. Spend this mana only to cast Myr spells or activate abilities of Myr.
{3}, {T}: Return target Myr card from your graveyard to your hand.

Myr Custodian

When Myr Custodian enters the battlefield, scry 2. Then each opponent may scry 1. (To scry X, that player looks at the top X cards of their library, then put any number of them on the bottom and the rest on top in any order.)

Sarcomite Myr

{2}: Sarcomite Myr gains flying until end of turn.
{2}, Sacrifice Sarcomite Myr: Draw a card.