Who is Alaizabel Cray from The Haunting of Alaizabel Cray and what is their importance?

Alaizabel Cray is a beautiful young woman, found by Thaniel Fox in London's Old Quarter. At that time Alaizabel was possessed and deranged, and she clawed at Thaniel. She is blonde, with green eyes and a tattoo of a many-tentacled thing at the base of her spine.

At first Alaizabel remembers nothing about her past. She feels alone in the world until she falls in love with Thaniel. Over the course of the novel, Alaizabel, Thaniel, and Cathaline learn about her past, especially about her parents' involvement with the Fraternity. Her parents were ultimately murdered and thrown in the Thames, and then Alaizabel was used by the Fraternity as a vessel for the spirit of the evil wych, Thatch. After the spirit of Thatch is finally removed from Alaizabel, vestiges of Thatch's power remain, especially the ability to cast spells known as Wards. Alaizabel is very brave, able to cope with the notions of being kidnapped several times, being possessed, suddenly developing wych powers, and fighting against the Fraternity.