Urza's Power Plant

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

Arcbound Crusher

Trample
Whenever another artifact enters, put a +1/+1 counter on Arcbound Crusher.
Modular 1 (This creature enters with a +1/+1 counter on it. When it dies, you may put its +1/+1 counters on target artifact creature.)

Snow-Covered Wastes

Abstruse Archaic

Vigilance
{1}, {T}: Copy target activated or triggered ability you control from a colorless source. You may choose new targets for the copy. (Mana abilities can't be targeted.)

Sol Ring

Urza's Tower

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

Arcbound Stinger

Flying
Modular 1 (This creature enters with a +1/+1 counter on it. When it dies, you may put its +1/+1 counters on target artifact creature.)

Hedron Crawler

{T}: Add {C}. ({C} represents colorless mana.)

Wayfarer's Bauble

{2}, {T}, Sacrifice Wayfarer's Bauble: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Chainbreaker

Chainbreaker enters with two -1/-1 counters on it.
{3}, {T}: Remove a -1/-1 counter from target creature.

Arcbound Bruiser

Modular 3 (This creature enters with three +1/+1 counters on it. When it dies, you may put its +1/+1 counters on target artifact creature.)

Alloy Myr

Urza's Fun House

{T}: Add {C}.
{T}: Add {∞}. Activate only once and only if you control an Urza's Mine, an Urza's Power-Plant, and an Urza's Tower.
{7}, {T}: Head to AskUrza.com and click Urza's Fun House.

Urza's Mine

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

Cathodion

Arcbound Slith

Whenever Arcbound Slith deals combat damage to a player, put a +1/+1 counter on it.
Modular 1 (This creature enters with a +1/+1 counter on it. When it dies, you may put its +1/+1 counters on target artifact creature.)