BRINGERS OF JUSTICE

Use this Stratagem when CUSTODES unit from
your army is chosen to attack in the Fight phase.
Each time you make a hit roll of 6+ for a model
in that unit during this phase it can if it was targeting a HERETIC ASTARTES unit, immediately make an extra attack against
the same unit using the same weapon. If it was targeting a BLACK LEGION unit, it instead
makes an extra attack on a hit roll of 4+. These
extra attacks cannot themselves generate further attacks.