Given the fact that Vorcan Radok is Mistress of the Assassins' Guild I would assume that there would be some explanation as to where did she come from. Is there more Vorcan Radok's character expansion?
There are definitely details in Esselmonts books. Nothing too revealing yet, but you do learn about he Cabal, Vorcan, and her daughter (although maybe not exactly what they are, in a way), which is part of Darujhistan's ancient history, although not as far back as Raest, I believe. Man, I gotta go re-read those books again in time for E's new novel to come out..