Madame Velix is a Geisterdame who seems to be the person in charge at an opera house in Paris. She is evidently undercover, as she wears a blue suit rather than traditional Geisterdamen clothing, although the garment incorporates some of their restrictive "criss-cross" motif into its design. When she is first introduced, there is a pair of goggles equipped with fake pupils lying on her desk, perhaps enabling her to pass as an albino human.
The opera house is staging a production about the Queen of the Dawn, and Velix's collar-insignia openly identifies her as working for Her Highness.
Unwelcome because Velix is also involved with, if not leading, a conspiracy to smuggle large amounts of miniaturized slaver-wasp hive engines into Paris, presumably to be used to enslave the entire city's population. She is working in some capacity with The King of the Silver Lands, and personally assists in his attempted of the Immortal Library of the Grand Architect. (Not to mention sharing more of his general hamminess than has been seen in her fellow Geisters to date.) In the process of this, she is by Larana Chroma and the hive engine which she has been lugging around is scooped up (or at least pointedly noticed) by Dimo.