Birthing Sporesac

{p/g}{p/g}{1}{t}:Put two -1/-1 counters on target creature. Activate only as a sorcery.
Whenever a creature dies if it had -1/-1 counters equal to or greater than its toughness search your library for a creature card with mana value equal to 1 plus that creature's mana value, put that card onto
the battlefield, then shuffle.