cumulative upkeep—flip a coin. (at the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
whenever you win a coin flip, karplusan minotaur deals 1 damage to any target.
whenever you lose a coin flip, karplusan minotaur deals 1 damage to any target of an opponent's choice.