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 - $3.60
Lightly Played - $3.30
Moderately Played - $2.90
Heavily Played - $2.60
Damaged - $1.80
NM-Mint Non English - $3.60
Lightly Played Non English - $3.30
Moderately Played Non English - $2.90
Heavily Played Non English - $2.60
Damaged Non English - $1.80