Crystal Henge of peace

If this card is in your starting hand you may play it without paying its mana cost
At the beginning of your end step, if you didn't attack this turn you may put a passive counter on Crystal Henge of peace. if you attacked this turn remove all passive counters from Crystal Henge of peace.
on your opponents turn you may prevent all damage that would be dealt to you and permanents that you control that turn if you have 3 or more passive counters on Crystal Henge of peace