At the beginning of each upkeep, put a strife counter on Crescendo of War. Attacking creatures get +1/+0 for each strife counter on Crescendo of War. Blocking creatures you control get +1/+0 for each strife counter on Crescendo of War.
NM-Mint - $2.50
Lightly Played - $2.20
Moderately Played - $2.00
Heavily Played - $1.70
Damaged - $1.30
NM-Mint Non English - $2.50
Lightly Played Non English - $2.20
Moderately Played Non English - $2.00
Heavily Played Non English - $1.70
Damaged Non English - $1.30