Bellatrix delved into darkness.
Whenever she came to the library to study, she ended up hanging around the Restricted Section like a shadow – and then she would throw fits for being denied access. Her boyfriend – her fiancé – would smirk and then restrain her. So many curses, on the librarian, would get her expelled.
She needed control – or to be controlled.
Her sisters were busy with their little lives. Narcissa was full of her own importance as a pretty pureblood princess and Andromeda was brooding over God knows what. Bella saw further than that. She needed absolute.
She would get it.