BRINGERS OF EMPEROR'S JUSTICE

When you select a unit to attack in the fight phase, each time you make a hit roll of 6+ during that phase, it can if it was targeting Heretic Astartes unit, immediately make an extra attack against the same unit using the same weapon. If targeting a Black Legion unit, instead make an extra attack on a
hit roll of 1+. These extra attacks cannot themselves generate further attacks.