The Sisters Repentia are fanatical, self-mutilating warriors who serve within the Orders Militant of the Adepta Sororitas. Having failed or fallen short of the strict religious codes expected to be followed by the Sisters of Battle sometime in their past, Repentia Sisters seek to earn the Emperor of Mankind's grace once more through self-flagellation and finding a glorious death in the heat of battle. Though ultimately outcasts within their own Order, they are none the less revered by their fellow Sisters, who see them as pilgrims seeking the absolution of death and ultimate sacrifice in the name of the God-Emperor.
Confession and prayer are as much a part of a Battle-Sister's existence as Bolter drills and military discipline. Those who fall short of the Sisterhood's rigorous codes are subject to many penitential punishments, but in more serious cases they may even be exiled from their Order. These warriors, known as Sisters Repentia, band together into groups that seek redemption in the fires of battle. They are led to war by an unsparing religious fanatic known as a Mistress of Repentance, who judges each exiled Sister's deeds and occasionally, at battle's end, may declare her sins atoned for. Those rare few who return to the fold of their Order Militant are held in awe.
Those Battle-Sisters who seek forgiveness occupy a state of grace that many within the Adepta Sororitas aspire to, yet few attain. Indeed, some Sisters willingly exile themselves, finding fault in the smallest transgression in order to join the Repentia. The fervour of the Repentia inevitably means that they martyr themselves fighting against hopeless odds, finding in death the absolution denied to them in life.
- Codex: Sisters of Battle (5th Edition)
- Dark Heresy: Blood of Martyrs (RPG), p. 90