His Fair Assassin Series by Robin LaFevers

Why be the sheep, when you can be the wolf? Seventeen-year-old Ismae escapes from the brutality of an arranged marriage into the sanctuary of the convent of St. Mortain, where the sisters still serve the gods of old. Here she learns that the god of Death Himself has blessed her with dangerous gifts—and a violent destiny. If she chooses to stay at the convent, she will be trained as an assassin and serve as a handmaiden to Death. To claim her new life, she must destroy the lives of others... moreWhy be the sheep, when you can be the wolf? Seventeen-year-old Ismae escapes from the brutality of an arranged marriage into the sanctuary of the convent of St. Mortain, where the sisters still serve the gods of old. Here she learns that the god of Death Himself has blessed her with dangerous gifts—and a violent destiny. If she chooses to stay at the convent, she will be trained as an assassin and serve as a handmaiden to Death. To claim her new life, she must destroy the lives of others. Ismae’s most important assignment takes her straight into the high court of Brittany—where she finds herself woefully under prepared—not only for the deadly games of intrigue and treason, but for the impossible choices she must make. For how can she deliver Death’s vengeance upon a target who, against her will, has stolen her heart? less

When Sybella arrived at the doorstep of St Mortain half mad with grief and despair the convent were only too happy to offer her refuge - but at a price. The sisters of this convent serve Death, and with Sybella naturally skilled in both the arts of death and seduction, she could become one of their most dangerous weapons. But her assassin's skills are little comfort when the convent returns her to the life that nearly drove her mad... moreWhen Sybella arrived at the doorstep of St Mortain half mad with grief and despair the convent were only too happy to offer her refuge - but at a price. The sisters of this convent serve Death, and with Sybella naturally skilled in both the arts of death and seduction, she could become one of their most dangerous weapons. But her assassin's skills are little comfort when the convent returns her to the life that nearly drove her mad. Her father's rage and brutality are terrifying, and her brother's love is equally monstrous. But when Sybella discovers an unexpected ally she discovers that a daughter of Death may find something other than vengeance to live for... less

Annith has watched her gifted sisters at the convent come and go, carrying out their dark dealings in the name of St. Mortain, patiently awaiting her own turn to serve Death. But her worst fears are realized when she discovers she is being groomed by the abbess as a Seeress, to be forever sequestered in the rock and stone womb of the convent. Feeling sorely betrayed, Annith decides to strike out on her own. She has spent her whole life training to be an assassin... moreAnnith has watched her gifted sisters at the convent come and go, carrying out their dark dealings in the name of St. Mortain, patiently awaiting her own turn to serve Death. But her worst fears are realized when she discovers she is being groomed by the abbess as a Seeress, to be forever sequestered in the rock and stone womb of the convent. Feeling sorely betrayed, Annith decides to strike out on her own. She has spent her whole life training to be an assassin. Just because the convent has changed its mind doesn't mean she has... less