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 - $41.20
Lightly Played - $39.10
Moderately Played - $37.10
Heavily Played - $33.00
Damaged - $26.80
NM-Mint Non English - $41.20
Lightly Played Non English - $39.10
Moderately Played Non English - $37.10
Heavily Played Non English - $33.00
Damaged Non English - $26.80