Misery, Who So Adores Company

As long as Misery, Who So Adores Company is in your graveyard, creatures you control have "{b}: Sacrifice this creature."
If Misery, Who So Adores Company is in your graveyard, whenever a creature you control dies, put a -1/-1 counter on each creature. Then, if you have six or more creatures in your graveyard, shuffle Misery into your library.