Emperor Emhyr had once presented the mages of Nilfgaard with a simple choice: either serve their country unquestioningly or die in prison.
Fringilla Vigo, a mistress of magic holding office in the vassal duchy of Toussaint, refused both options and instead joined the infamous Lodge of Sorceresses, whose aim was to stand up to the dictates of kings and emperors. These bold ambitions were never fulfilled, however, and Fringilla Vigo lived in fear that her ties to this subversive organization would be discovered and she would meet a quick end at the hands of the emperor's executioners.
One must mention here that Geralt first met Fringilla at the ducal palace in Beauclair many years ago, when we were there enjoying the hospitality of my one-time love, Duchess Anna Henrietta. The witcher, always a sucker for sorceresses, conjoined with Madame Vigo during this time in a quite lively relationship that surely was no cause of joy for Triss or Yennefer.
All indications were that Fringilla had been arrested and remained in a Nilfgaardian prison, undoubtedly awaiting execution for acts of high treason.