Margaret

Margaret is the aunt of September and the sister of Susan Jane.

History
Aunt Margaret was first mentioned in book 1 by the Green Wind, who used the analogy of a puzzle ring brought by her from Turkey being akin to the geography of the world.

She later appears in person in book 4, when she comes to the aid of her worried sister.

Later in book 5, in order to help Susan Jane look for September, Margaret reveals that she knows that the girl is in Fairyland, having gone there herself in her youth with the aid of the Green Wind. She then shows that the puzzle ring previously mentioned by the Green Wind is her magical means into Fairyland, allowing her at her older age to enter the land whenever she so wished. Margaret then proceeds to take September's parents into Fairyland to search for their lost daughter. They arrive in the Painted Forest, which had been created by Tamburlaine. There they meet six hippos, which Margaret had previously created out of stuff she had brought with her from the human world.

Later, when they were resting at the Peppercorn Pyramids, they were attacked by two blue lions, the very same that had been in service to the Marquess. But, upon seeing Margaret, the lions both cowered, calling her "Madame Pearl", revealing her identity as Pearl the Thaumaturge, the very same girl who had turned all the Fairies on the Moon into tools.

Finally she, her sister, and brother in law arrive in Pandemonium, just as September was killed, and later meet her when she was revived as the Green Wind and came back to the Briary. She also had turned Tanaquill into the Tobacconist's throne.