Murderous Perfection

The desire for perfection that drives Slaanesh's
warriors is such that their fighting skills far exceed
those of more blinkered forces - an obsessive drive
that leads to superior acts of martial precision.
Use this Stratagem in your Shooting or the
Fight phase, when a Traitoris Astartes Slaanesh
unit from your army is selected to shoot or fight.
Once during that phase, when resolving an
attack made by a model in that unit, you can
change the result of one hit, wound or damage
roll