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 - $1.40
Lightly Played - $1.20
Moderately Played - $1.10
Heavily Played - $1.00
Damaged - $0.70
NM-Mint Non English - $1.40
Lightly Played Non English - $1.20
Moderately Played Non English - $1.10
Heavily Played Non English - $1.00
Damaged Non English - $0.70