Scavenger of the Bog

Whenever Scavenger of the Bog is put into your graveyard from anywhere, shuffle your graveyard into your library, then put Scavenger of the Bog onto the top of your library.
At the end of each upkeep pay {p/g}{p/g} or {p/b}{p/b} or sacrifice Scavenger of the Bog. If you do, put five +1/+1 counters on Scavenger of the Bog.