Hannah is the maid of the Trancy Household.

Hannah has rather tan skin with slanted bluish-purple eyes and wears purple lipstick. Her hair is a very pale violet-blue that extends far down her back, and the second half of it is braided. She is a rather busty woman, and wears a long blue and white maid dress with an accompanying plate-shaped maid cap.

Hannah is loyal to her master, Alois Trancy, and is quite a mysterious woman. She seems to be quite a worried person, and is often seen with her head tilted down as a way of avoiding eye contact with others. She is quite obviously terrified of Alois, and is calm except for the moments in which he is speaking to her. In these moments, she is brisk, nervous, and will even tremble with fear.

Hannah is actually a demon, and the reason Alois' village burned to the ground (Luka asked her to destroy the townspeople and the village for his brother's sake). As such, she began to feel Luka's feelings of love for Alois, so she became his servant, having grown tired of her life as a demon. She is also known as the Sheathe for Lævateinn, which is a demon blade that can inflict a wound upon a demon that is incapable of being healed. She grants Alois' wish when he wishes to turn Ciel into a demon. She dies next to Claude, saying that she, Claude, Luka and Alois can now be together.
(Source: Kuroshitsuji Wikia)