Roberto told the Doctor that Madame Xing was an offworlder to Espero. He said that no one knew her true name, because it was unpronounceable.
Xing claimed to be a viropractor, specialising in the use of viroids to alter and enhance cognitive development and memory. She helped the Doctor restore the memories of his arrival on Espero. She then offered to restore the remainder of his memories, to which he refused. (PROSE: Halflife)
Behind the scenes
- Madame Xing is strongly implied to be Compassion: she knows who the Doctor is; she knows about the Time Lords despite their erasure from history; and she's implied to be dimensionally transcendental. The Gallifrey Chronicles would later suggest that her goal in restoring the Doctor's memories was to prevent the return of the Time Lords.
- Xing might also be Countess Gallowglass from the author's previous novel, Relative Dementias; in his short story Commune, published in the 2003 fanzine Myth Makers 13, he established that a colony of Time Lords had been living in an implant in her head since Gallifrey's fall in The Ancestor Cell.