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.
Near Mint - $600
Lightly Played - $500
Moderately Played - $400
Heavily Played - $400
Damaged - $300
Near Mint Spanish - $600
Lightly Played Spanish - $500
Moderately Played Spanish - $400
Heavily Played Spanish - $400
Damaged Spanish - $300