At the beginning of each upkeep, count the number of permanents. If the number is odd, until end of turn, red creatures get +1/+1 and whenever a player taps a Mountain for mana, that player adds an additional {R}. If the number is even, until end of turn, red creatures get -1/-1 and if a player taps a Mountain for mana, that Mountain produces colorless mana instead of any other type.
Near Mint - $0.95
Near Mint Non-English - $0.95
Lightly Played - $0.90
Lightly Played Non-English - $0.90
Moderately Played - $0.76
Moderately Played Non-English - $0.76
Heavily Played - $0.57
Heavily Played Non-English - $0.57
Damaged - $0.47
Damaged Non-English - $0.47