Repair the Oxygen!

At the start of any players upkeep, they take {x} damage, where {x} is the amount of
asphyxiation counters they have.
Task 2, {t}: All players gain 1 asphyxiation
counter.
Task 5, {2}{t}: Destroy any amount of asphyxiation counters, then destroy a target nonland
permanent that has a converted man a cost that
equals the amount of tokens destroyed.