Chloé d'Apchier is a vampire who serves as a central figure in the Gévaudan arc of the narrative. Residing in the district of Gévaudan within what is known as the Silver Forest, she is often referred to as the Silver Witch. Despite her appearance as a young girl with curly, pale gray hair and grayish-blue eyes, she is actually over two hundred years old, making her one of the oldest vampires in existence. Her physical growth stopped when she was eleven, a side effect of her transformation from human to vampire. Originally born as a human daughter to the noble d'Apchier family, she became a vampire at the age of four following the Babel Incident. Because of her condition, her death was faked, and she was forbidden from leaving her family home or revealing her face. Her father, desperate to find a cure, began researching the World Formula without the Church's permission, a pursuit that continued for generations and eventually shifted toward political gain.

Chloé's personality is complex, shaped by centuries of isolation and loss. While she possesses the maturity and knowledge befitting her great age, she is also deeply lonely and sorrowful. She cries every day, having watched over the d'Apchier family and the people of her territory for an immense span of time, only to witness ruin and massacre. Despite her circumstances, she retains a strong sense of duty, determined to follow her father's words and protect the people of the territory even when she harbored personal anguish. Her calm and collected demeanor often masks her intense emotions, and she is capable of great cunning, as shown when she feigned cooperation with Naenia for the sole purpose of exacting revenge for the tarnishing of Jean-Jacques Chastel's name. She is not inherently malevolent; her actions as a curse-bearer stem from a wish for revenge and a desire to end her suffering, though she ultimately craves nothing more than to be looked upon innocently and sincerely by others.

Her primary motivation throughout the Gévaudan incident is revenge. She willingly gave up her true name and became a curse-bearer after making a deal with Naenia, the malnomen of Charlie, in exchange for a wish. This decision was spurred by the murders of her biological family members and the subsequent scorn from her remaining family, culminating in a deep-seated desire for vengeance against Naenia, who she felt had defiled the name of her one and only special person, Jean-Jacques. Her role in the story is that of the supposed Beast of Gévaudan, an antagonist whose curse and actions drive the collaborative effort between humans and vampires to hunt her. However, her true role is more tragic; she is a victim of circumstance who ultimately resists her own destructive rampage when reminded of genuine love and connection.

Key relationships define much of Chloé's history and development. Her first vampire acquaintance was August Ruthven, a teacher and moderate during the war, with whom she became friends. He later entrusted her with the care of a young Jeanne, the daughter of two of his students. Chloé disobeyed her family's orders to hide herself for Jeanne, and the two developed a deep, sisterly bond of love and care. Chloé taught Jeanne various subjects and games during this time. Their relationship became tragic when Jeanne, now an executioner known as the Bourreau, was assigned to kill the Beast of Gévaudan, not knowing it was Chloé. Chloé is also deeply connected to Jean-Jacques Chastel, a young vampire boy she took in after finding him abused by his human parents. He so cherished Chloé that he gave his true name to Naenia to become the Beast of Gévaudan himself, believing it would stop the murders and protect her. Chloé views Jean-Jacques as her one and only special being, and his defilement is what drives her desire for revenge.

Chloé undergoes significant development, transitioning from a lonely, secluded vampire to a willing curse-bearer bent on revenge, and finally to a person who chooses life and connection. After being forced out of control by Queen Faustina's kiss, her malnomen reaches its most dangerous state, stripping away her reason and turning her into a formless, destructive fog-like apparition. In this state, she acts mindlessly with the intent to destroy herself and everything around her. However, witnessing Jean-Jacques' earnest desire to live together and seeing both him and Jeanne rush to save her without hesitation awakens the sincerity she had forgotten. She recalls that she simply wanted someone to look at her innocently, regardless of her nature as a vampire. Leaping into their embrace, she resists the runaway power, ultimately allowing Vanitas to cure her.

Chloé possesses formidable abilities that reflect her immense age. As a vampire, her physical strength, speed, and endurance far surpass those of humans, enhanced by interference with the World Formula. Despite her childlike body, she can easily overpower an adult man, rendering him unconscious with a single slap, and can send out energy whips that slash and tear through her surroundings. Her most notable ability is her mastery of the World Formula Alteration Device, a machine the d'Apchier family spent centuries developing. As the longest-living member of her family, she knows how to use it better than anyone, rewriting the World Formula to carry out her bidding and even force a physical form upon Naenia. Her malnomen, which she contracted willingly, is named Millie, Theater of Ice and Snow. This curse's primary power is to create an enclosed space that holds an entire closed world generated from the memories of those infected, even recreating people based on how Chloé remembers them. When advanced to its peak, the malnomen grants her additional destructive abilities, including the power to scramble gravity, lift chunks of earth, and create wolf-shaped familiars from black mist to do her bidding.