In the context of Selina Mandrake - The Slayer, Kate (known in the past as Kate Hampshire, Lady Kate Canterson, Mrs. Kate Black, and eventually Prof. Kate Hampshire) is a vampire, who is notable for having slain Lord Buckingham (later known as George), and the more real-life equivalent of Milady de-Winter from Alexandre Dumas’s The Three Musketeers.
Kate helped slay Lord Buckingam/George by faking his death, and arriving with him to the British colonies in North America, where they both started a new life. Eventually, Kate was indoctrinated as a vampire, which in the context of the “Selinaverse” is actually a benevolent individual, who spreads and inspires happiness and success, does not age in mind, and, in some cases, continues to live forever in the same body and soul.
After the publication of The Three Musketeers, Kate was identified as the real-life version of The Slayer (whereas Milady de-Winter is a more global and ideal The Slayer), and was contacted about “slaying” more people. She ended up travelling to meet Dumas and after expressing her frustration and introducing what she was in a previous life, was given the advice of simply refusing to slay any subsequnet people, which she did.
Nevertheless, Kate looked forward to being superseded by The Dispeller, which was considered the next logical level after slaying, where The Dispeller turned out to be Selina Mandrake, the protagonist of the screenplay.
As the screenplay ends, Kate is revealed to have a Ph.D. in Biblical studies (owing to her life long obsession with the Bible) and is an active lecturer and researcher (having a professorship) in the field, and agrees to help Selina in learning Cuneiform.