A Penitent Bride who is as surly as she is beautiful, Charlotte is quick to anger but hides her emotions behind a mask of neutrality. She is surprisingly shy when it comes to matters of the heart, feeling awkward and flustered when put on the spot. Not much one for small talk, she usually stalks off when approached by strangers as her social skills are lacking, especially in comparison to Father Valentine's. She is wholly uninterested in forging new relationships with others, though she finds herself repeatedly getting stuck with an everchanging roster of new people in her life.

While withdrawn and a bit cold, she still has a large heart but, because of her past, she prefers to keep people away, as she is quite emotionally frail and tender-hearted, though she hides it behind a blank and passive facade. Through meeting and working with Nathaniel, Dominic, and Ven, she chooses to become more expressive and allows herself to demonstrate her naturally nurturing character more often.

Though serious and a bit brooding, Charlotte still maintains a dry sense of humor and often plays along when Nathaniel is feeling playful. Because of her religious upbringing and growing up in an all-girls environment, she reacts shockingly bashful to Nathaniel's flirtatious antics or Sister St. Patrick's salacious remarks. She prefers order and procedure——when her routine of cleaning her guns after a hunt gets interrupted, she gets irritable and moody.

Charlotte specializes in the removal of malevolent ghosts and demons and prides herself in her skill. She can usually be found studying or training with the other Sisters at the Penitent Bride convent when not on a mission.

Born as Maria Luiza da Silva, Sister Charlotte Halloween grew up in a large and loving family in Portugal. She was orphaned at a young age and placed into the care of Our House of Lady Fátima, a church-run orphanage and boarding school for lost and troubled girls.

As an adolescent, Charlotte grew quite the temper but relied on her faith to keep her steady. The head nun, Sister Catarina, noticed her unyielding faith and rigourous discipline——brutally steadfast in her beliefs——and nominated her as a candidate to join the renowned yet esoteric convent that trained Penitent Brides. She trains hard and studies dutifully for years, and with nothing of a family or home life to distract her, Charlotte excels. As tradition, she is christened with a new name¹ as she takes on the mantle of Sister Charlotte Halloween once she has earned her place amongst the ranks of the Penitent Brides.

Charlotte befriends Sister Niamh St. Patrick, and holds her, along with the other Sisters at the Brides convent dear to her heart, though she rarely expresses it.

Charlotte and Nathaniel are granted a rare dispensation from the Church after taking down The Black Herald. They spend the rest of their days living peacefully in the French countryside, often writing letters to Dominic who is now in the Americas. They run a small books and curiousities shop, and it is rumoured by the townsfolk that the surprisingly elaborate garden in the courtyard was planted by the shop curator in tribute of his wife's family.