|Weapon||Vectors, Black Blood|
One of the occupants of the Phantomhive Mansion and the offspring of Medusa Gorgon and Grell Sutcliff. Borealis has been experimented and injected with Black Blood and DNA derived from a sample of Anna Sanctimonia's tissue. Due to the extreme difference of the parents' identity, Borealis' body houses different souls, which gives her distinctly different personality when one soul is dominant over others.
Derived from Medusa's witch soul which became the main soul of Borealis, as it is the first to be able to take control of the body. However, she is extremly ignorant, much like a child.
Derived from Grell Sutcliff's soul. Australis takes on the responsibility of taking care of Borealis and the body, as if she was the guardian of her.
Derived from the corruption within Anna, she is sadistic and violent. She does not usually take control of the body outside of combat.
Derived from Anna's soul, she is a friendly person, and wants to help others whenever she can. Usually takes control of the body when someone is hurt or injured.
The father of Borealis, however, due to Grell's personality, he teaches Borealis to refer to him as "Mommy". Borealis is the only one who calls Grell "Mommy", the others usually refer to him either by Grell or Mr.Sutcliff.
The mother of Borealis, who occasionally conducts experiments on her body. Borealis understands that Medusa is her mother, and follows her orders without questions. Though Borealis does not enjoy being experimented on, she does not complain either. Australis, who would disapprove the experiments, sees it as a way for the body to become stronger, and does not object.
The godmother of Borealis, who shares a portion of her genes to Borealis, due to Medusa's request, as it would improve the efficiency of Black Blood within Borealis' body. Because of the gene injection, two new souls takes place in Borealis' body, which were named Zephyralis and Eurualis.
The half-brother of Borealis, who soughts to help Borealis with her black blood. As another user of the black blood, he tries to warn Borealis of the misfortune he had gone through due to the nature of black blood. Crona strongly opposes Medusa's experiments on Borealis, and attempts to take responsibility for her, away from Medusa's hands.