Countercard War

Whenever an opponent casts a spell or plays a
land, make a nonland permanent card that will conflict that spell or land and cast it without
paying its mana cost. Then, your opponent also
makes a card that will conflict the card you just
made. Continue this process until either you or
the opponent wish to stop. When either one of
you do, counter each spell apart from the card on
the top of the stack and if this ability was
triggered by a land entering the battlefield, exile
it and all gra