Sanguine Rites

As an additional cost to cast Sanguine Rites, sacrifice a creature and pay 4 life.
Reveal the top X cards of your library, where X
is equal to the life you've lost this turn. You may
put a creature card from among them into your
hand. Shuffle the rest into your library. Then
add {b} to your mana pool for each creature that
died this turn. Spend this mana only to cast
creature spells found this way.