You get approached by a number of her Vamp's roaming the city killing and recruiting shadow thieves....it doesnt matter if you get the offer from Gaelan Bayle..actually its the only thing you can do.
After a period of time, Valen asks you to go see his/her? mistress at the graveyard after dark. I havent been able to find her so far (stupid friggin vamps..never come out when you want them too
). I hope i cleared that up for U