Ninja Strike 4 (Whenever one of your opponent's creatures attacks or blocks, if you have 4 or more cards in your mana zone and if during that attack you didn't use a "Ninja Strike" ability, you may summon this Shinobi for no cost. At the end of the turn, put this Shinobi on the bottom of your deck.)
When you put this creature into the battle zone, one of your creatures gets "blocker" until the start of your next turn.