Sisters of Battle Special Rules
Shield of Faith
The Adepta Sororitas represent the epitome of faith and purity — witchcraft, heresy and mutation are anathema to them. Force weapons lose their ability to kill their target outright, simply count them as power weapons. Psychic powers targeted against any unit or character with the Adepta Sororitas special rule, or including them in its area of effect, are nullified and will not work on a D6 roll of 5+ (roll once for each power, even if it affects several Adepta Sororitas units).
Minor psychic powers have no effect on Adepta Sororitas units or characters at all, even those used by friendly psykers that would have a beneficial effect on them.