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 - £0.70
Lightly Played - £0.60
Moderately Played - £0.50
Heavily Played - £0.40
Damaged - £0.20
Near Mint Non English - £0.70
Lightly Played Non English - £0.60
Moderately Played Non English - £0.50
Heavily Played Non English - £0.40
Damaged Non English - £0.20