[Source] Carthia van Canten, also known as "Cantarella" and ""Sasha"", was the mistress of Vattier de Rideaux, the head of Nilfgaardian intelligence for Emhyr var Emreis. She was informing Assire var Anahid about Vattier's intentions. She had an excellent memory, a lively intelligence, and a mercurial wit.