Ultimate Gamble

Target opponent pays any amount of mana, then
you must pay that the same amount. If you can't
you lose {x} life where {x} is the mana the
opponent payed. If you are able to pay the
same amount, roll a 20 sided die.
If the result is even, your life becomes equal to
the result of the roll. If the result is odd,
opponent's life becomes equal to the result of the
roll.