If no one knew you couldn't aparate inside the walls of Hogwarts, Slytherin house would have thought Hecate merely appeared there. But she was just sneaky.

"Attention Students." She said glaring at the table... Why was it that other houses saw fit to go and sit at other houses tables? "I have a few announcements to make," she told them and then emphasized, "for the Great House of Salazar Slytherin."