Ellroy, Spirit Herder

{b}{g}, Sacrifice a nontoken creature: Reveal cards
from the top of your library until you reveal a
creature card. Put that card into your hand and
the rest on the bottom of your library in a random
order. If this is the third time this ability has
resolved this game, you may summon Szass,
Unhallowed Reaper. (You may put Szass,
Unhallowed Reaper into play from your exile zone.)