Unwinding Clock

Untap all artifacts you control during each other player's untap step.

Plains

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.

Urza's Tower

{T}: Add {C}. If you control an Urza's Mine and an Urza's Power-Plant, add {C}{C}{C} instead.

Steel Overseer

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

Door of Destinies

As Door of Destinies enters, choose a creature type.
Whenever you cast a spell of the chosen type, put a charge counter on Door of Destinies.
Creatures you control of the chosen type get +1/+1 for each charge counter on Door of Destinies.

Myr Kinsmith

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

Tempered Steel

Artifact creatures you control get +2/+2.

Arrest

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

Urza's Power Plant

{T}: Add {C}. If you control an Urza's Mine and an Urza's Tower, add {C}{C} instead.

Dispatch

Tap target creature.
Metalcraft — If you control three or more artifacts, exile that creature.

Plague Myr

Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
{T}: Add {C}.

Urza's Mine

{T}: Add {C}. If you control an Urza's Power-Plant and an Urza's Tower, add {C}{C} instead.

Welding Jar

Sacrifice Welding Jar: Regenerate target artifact.

Scourglass

{T}, Sacrifice Scourglass: Destroy all permanents except for artifacts and lands. Activate only during your upkeep.

Myr Galvanizer

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

Hovermyr

Gold Myr

Demystify

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.

Forsaken Monument

Colorless creatures you control get +2/+2.
Whenever you tap a permanent for {C}, add an additional {C}.
Whenever you cast a colorless spell, you gain 2 life.

Expedition Map

{2}, {T}, Sacrifice Expedition Map: Search your library for a land card, reveal it, put it into your hand, then shuffle.

War Report

You gain life equal to the number of creatures on the battlefield plus the number of artifacts on the battlefield.