Hidden Necropolis

This land enters tapped.

{t}: Add {b}.

{4}{b}, {t}, Sacrifice this land: Discover 4. Activate only as a sorcery. (Exile cards from the top of your library until you exile a nonland card with mana value 4 or less. Cast it without paying its mana cost
or put it into your hand. Put the rest on the bottom
in a random order.)