Aetherflow Grove

Hideaway (This land enters the battlefield tapped. When it does, look at the top four cards of your library, exile one face down, then put the rest on the bottom of your library.)
{t}, Pay 1 life: Add {u} or {g} to your mana pool.
{g/u}, {t}: You may cast the exiled card without paying its mana cost if you control eight or more basic lands.