Professor Septima Vector is a minifigure which appears in LEGO Harry Potter: Years 1-4. She is the Professor of Arithmancy at Hogwarts. Not much is known about her, but arithmancy, the study of numbers and their impact on the future, is apparently Hermione's favorite subject. Hermione says she doesn't give much homework.
In the game, you find her token (how you unlock characters in the game.) in the scene "Tom Riddle's Diary."