Malediction, the dark messiah.

Into the Penumbra -Whenever you cast a black
sorcery give target creature shroud until
Malediction leaves the battlefield
Means to the end - If you control
five or more permanents with shroud you may
sacrifice Malediction, the Dark Messiah.
If you do, so search your library for a black
creature card, you may play it without paying
the mana cost.