Viseling

At the beginning of each opponent's upkeep, Viseling deals X damage to that player, where X is the number of cards in their hand minus 4.

Shimmer Myr

Flash
You may cast artifact spells as though they had flash.

The Grey Havens

When The Grey Havens enters, scry 1.
{T}: Add {C}.
{T}: Add one mana of any color among legendary creature cards in your graveyard.

Contagion Clasp

When Contagion Clasp enters, put a -1/-1 counter on target creature.
{4}, {T}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Karn, Living Legacy

+1: Create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")
−1: Pay any amount of mana. Look at that many cards from the top of your library, then put one of those cards into your hand and the rest on the bottom of your library in a random order.
−7: You get an emblem with "Tap an untapped artifact you control: This emblem deals 1 damage to any target."

Sting, the Glinting Dagger

Equipped creature gets +1/+1 and has haste.
At the beginning of each combat, untap equipped creature.
Equipped creature has first strike as long as it's blocking or blocked by a Goblin or Orc.
Equip {2}

Myr Galvanizer

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

Tomb of the Spirit Dragon

{T}: Add {C}.
{2}, {T}: You gain 1 life for each colorless creature you control.

Graaz, Unstoppable Juggernaut

Juggernauts you control attack each combat if able.
Juggernauts you control can't be blocked by Walls.
Other creatures you control have base power and toughness 5/3 and are Juggernauts in addition to their other creature types.

The Mycosynth Gardens

{T}: Add {C}.
{1}, {T}: Add one mana of any color.
{X}, {T}: The Mycosynth Gardens becomes a copy of target nontoken artifact you control with mana value X.

Urza's Factory

{T}: Add {C}.
{7}, {T}: Create a 2/2 colorless Assembly-Worker artifact creature token.

Brass Squire

{T}: Attach target Equipment you control to target creature you control.

Power Depot

Power Depot enters tapped.
{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast artifact spells or activate abilities of artifacts.
Modular 1

Prosthetic Injector

Equipped creature gets +0/+2 and has toxic 1. (Players dealt combat damage by equipped creature also get a poison counter.)
Equip {1}

Foundry Inspector

Artifact spells you cast cost {1} less to cast.

Steel Overseer

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

Ugin, the Ineffable

Colorless spells you cast cost {2} less to cast.
+1: Exile the top card of your library face down and look at it. Create a 2/2 colorless Spirit creature token. When that token leaves the battlefield, put the exiled card into your hand.
−3: Destroy target permanent that's one or more colors.

Bronze Sword

Equipped creature gets +2/+0.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Blinkmoth Well

{T}: Add {C}.
{2}, {T}: Tap target noncreature artifact.

Myr Scrapling

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

Meteor Golem

When this creature enters, destroy target nonland permanent an opponent controls.

Myr Kinsmith

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

Bone Saw

Equipped creature gets +1/+0.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Eriette's Tempting Apple

When Eriette's Tempting Apple enters, gain control of target creature until end of turn. Untap that creature. It gains haste until end of turn.
{2}, {T}, Sacrifice Eriette's Tempting Apple: You gain 3 life.
{2}, {T}, Sacrifice Eriette's Tempting Apple: Target opponent loses 3 life.

Cloak of the Bat

Equipped creature has flying and haste.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

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 Propagator

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

Myr Custodian

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

Myr Battlesphere

When Myr Battlesphere enters, 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.

Sword of Once and Future

Equipped creature gets +2/+2 and has protection from blue and from black.
Whenever equipped creature deals combat damage to a player, surveil 2. Then you may cast an instant or sorcery spell with mana value 2 or less from your graveyard without paying its mana cost. If that spell would be put into your graveyard, exile it instead.
Equip {2}

Tapestry of the Ages

{2}, {T}: Draw a card. Activate only if you've cast a noncreature spell this turn.

Myr Superion

Spend only mana produced by creatures to cast this spell.

Veil of Assimilation

Whenever Veil of Assimilation or another artifact you control enters, target creature you control gets +1/+1 and gains vigilance until end of turn.

Vanquisher's Axe

Equipped creature gets +2/+0.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Myr Sire

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

Darksteel Ingot

Indestructible (Effects that say "destroy" don't destroy this artifact.)
{T}: Add one mana of any color.

Kitesail

Equipped creature gets +1/+0 and has flying.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Ornithopter

Symmetry Matrix

Whenever a creature you control with power equal to its toughness enters, you may pay {1}. If you do, draw a card.

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

Myr Convert

Toxic 1 (Players dealt combat damage by this creature also get a poison counter.)
{T}, Pay 2 life: Add one mana of any color.

Myr Moonvessel

Drannith Ruins

{T}: Add {C}.
{2}, {T}: Put two +1/+1 counters on target non-Human creature that entered this turn.

Soulless Jailer

Permanent cards in graveyards can't enter the battlefield.
Players can't cast noncreature spells from graveyards or exile.

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Spidersilk Net

Equipped creature gets +0/+2 and has reach. (It can block creatures with flying.)
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Hero's Heirloom

Equipped creature gets +2/+1.
As long as equipped creature is legendary, it has trample and haste.
Equip {2}

Drillworks Mole

{2}, {T}: Put a +1/+1 counter on Drillworks Mole and a +1/+1 counter on up to one target commander creature you control.

Ash Barrens

{T}: Add {C}.
Basic landcycling {1} ({1}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Myr Enforcer

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

Soul-Guide Lantern

When this artifact enters, exile target card from a graveyard.
{T}, Sacrifice this artifact: Exile each opponent's graveyard.
{1}, {T}, Sacrifice this artifact: Draw a card.

Coretapper

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