Retrieve the Powers of the Void for Drusilla La Salle.
You there! [player], right?
I hope you're sure about becoming a warlock, because if you can't hold your own, you're likely to get pulled under.
I'm to teach you, but I need to make sure you're strong enough first.
There was a novice studying at the Abbey who ran off to join the Defias Brotherhood. Why do I care? Well, he stole some important books.
One of those happens to be a book I've wanted for myself, the Powers of the Void. Steal it for me, they have it hidden at their tent in the Vineyards.