Hidden Necropolis: Lost Caverns of Ixalan

Hidden Necropolis enters the battlefield tapped. {T}: Add {B}. {4}{B}, {T}, Sacrifice Hidden Necropolis: 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.)