Marble Diamond

Marble Diamond enters tapped.
{T}: Add {W}.

Gold Myr

Coldsteel Heart enters tapped.
As Coldsteel Heart enters, choose a color.
{T}: Add one mana of the chosen color.

Star Compass enters tapped.
{T}: Add one mana of any color that a basic land you control could produce.

At the beginning of each player's first main phase, if Blinkmoth Urn is untapped, that player adds {C} for each artifact they control.

Lands don't untap during their controllers' untap steps.
At the beginning of each player's upkeep, that player untaps a land they control.