Thought Vessel

You have no maximum hand size.
{T}: Add {C}.

Unwinding Clock

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

Urza's Rebuff

Choose one —
• Counter target spell.
• Tap up to two target creatures.

Seat of the Synod

Urza, Lord High Artificer

When Urza enters, create a 0/0 colorless Construct artifact creature token with "This token gets +1/+1 for each artifact you control."
Tap an untapped artifact you control: Add {U}.
{5}: Shuffle your library, then exile the top card. Until end of turn, you may play that card without paying its mana cost.

Sai, Master Thopterist

Whenever you cast an artifact spell, create a 1/1 colorless Thopter artifact creature token with flying.
{1}{U}, Sacrifice two artifacts: Draw a card.

Etherium Sculptor

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

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.