Grim Prospector

At the beginning of your upkeep, mill a card.
{t}, Exile two land cards from your graveyard:
Create a colorless artifact token named Gold. It
has "Sacrifice this artifact: Add one mana of any
color to your mana pool."
The prospector Grimm, with prospects a'grim, fell
afoul to forces profane. Refusing to spoil, he continues
to toil, ever scouring in vain for a vein.