When Phyrexian Devourer's power is 7 or greater, sacrifice it. Exile the top card of your library: Put X +1/+1 counters on Phyrexian Devourer, where X is the exiled card's mana value.
NM-Mint - $42.80
Lightly Played - $38.50
Moderately Played - $34.20
Heavily Played - $30.00
Damaged - $21.40
NM-Mint Non English - $42.80
Lightly Played Non English - $38.50
Moderately Played Non English - $34.20
Heavily Played Non English - $30.00
Damaged Non English - $21.40