Dwarven Vigilantes

Oracle Text

Whenever Dwarven Vigilantes attacks and isn't blocked, you may have it deal damage equal to its power to target creature. If you do, Dwarven Vigilantes assigns no combat damage this turn.

Card Rulings

4/15/2013 An ability that triggers when something “attacks and isn’t blocked” triggers in the declare blockers step after blockers are declared if (1) that creature is attacking and (2) no creatures are declared to block it. It will trigger even if that creature was put onto the battlefield attacking rather than having been declared as an attacker in the declare attackers step.