Echoes of Eternity

If a triggered ability of a colorless spell you control or another colorless permanent you control triggers, that ability triggers an additional time.
Whenever you cast a colorless spell, copy it. You may choose new targets for the copy. (A copy of a permanent spell becomes a token.)

Sol Ring

The Capitoline Triad

Those Who Came Before — This spell costs {1} less to cast for each historic card in your graveyard. (Artifacts, legendaries, and Sagas are historic.)
Exile any number of historic cards from your graveyard with total mana value 30 or greater: You get an emblem with "Creatures you control have base power and toughness 9/9."

Buried Ruin

{T}: Add {C}.
{2}, {T}, Sacrifice this land: Return target artifact card from your graveyard to your hand.

Urza's Mine

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

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.

Shimmer Myr

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

Sojourner's Companion

Affinity for artifacts
Artifact landcycling {2} ({2}, Discard this card: Search your library for an artifact land card, reveal it, put it into your hand, then shuffle.)

Null Elemental Blast

Choose one —
• Counter target multicolored spell.
• Destroy target multicolored permanent.

Thran Dynamo

Urza's Tower

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

Urza's Power Plant

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

Jhoira's Familiar

Flying
Historic spells you cast cost {1} less to cast. (Artifacts, legendaries, and Sagas are historic.)

Darksteel Citadel

Liberator, Urza's Battlethopter

Flash
Flying
You may cast colorless spells and artifact spells as though they had flash.
Whenever you cast a spell, if the amount of mana spent to cast that spell is greater than Liberator's power, put a +1/+1 counter on Liberator.

Myr Enforcer

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