Mystic Caverns

Mystic Caverns enters the battlefield tapped.
{t}: Reveal the top card of your library. Add one mana to your mana pool that is a color in the revealed card's color identity.
{x}, {t}: Look at the top X cards of your library. Put all but one of them into your graveyard.
Pockets of mana trapped in crystals give the caverns a peculiar array of colors.