"She was a tall blonde teenager in an English pub¬lic school uniform, complete with starched white blouse, black miniskirt and stockings, sensible shoes, and a straw boater perched on the back on her perfect head. She was bright and cheerful, heart-stoppingly pretty, far too shapely for her own good, or anyone else's, and moved with all the unrealised elegance of youth. She had a pink rosebud mouth, and eyes so dark they seemed to fall away forever."
As described by John Taylor.
She is the daughter of a demon succubus and hence her appearance is different to every onlooker; catered to their preferences. She is faster and stronger than any human being could ever be, besides she can use hell-magic.
Alex Morissey sees her as looking like his ex wife Agatha, but with bigger breasts.
First introduced in Hex and the City, we are told she has left the Inferno to come to earth "to try and understand this thing called ... true love." Towards the end of the novel, she places herself between her lover Sinner (who is madly in love with her) and the bullets being shot at him, finally understanding the concept of "love" she is returned to heaven along with "her Sidney."
Later, during Liliths war she is summoned by Dead Boy, Julian and John Taylor directly to nightside (which is normaly not possible) to help John get into the future to meet his old enemies. She also indicates that this is last favor she gives him and he´d better lose her "number".