I'm going mostly with your concept for my character. I'll probably post a history/description in the character background thread later.
For the master, I may as well keep the name you gave him, Incubus, since it's acceptable and I'm incredibly bad at coming up with names. (You can give him a more appropriate name if you like.) For concept, I think he is all about material gain. In his youth, before awakening, he began his climb to the top in the business world, with the sole goal of making himself very rich, in order to rise above his parents' near-subsistance level farming lifestyle. For many years after awakening, he used his magic to help him become more wealthy. Among other things, he was the first person ever to serve as CEO of 3 different Fortune 500 companies before he turned 40 (in succession, not simultaneously, of course). However, upon reaching middle age, he realized that he had all the money he could ever use, and could obtain more on a whim if it ever became an issue. So his new goal became accruing priceless artifacts. Of course he likes magical artifacts--since they often serve purposes other than just enhancing his collection, and are much more impressive to many of his peers, but he is personally interested in any priceless artifacts, and does not mind obtaining them in less than honest ways, and does not care who he hurts along the way. He hopes to use Sarah's talents to assist him in acquiring new additions to his collection (as well as whatever the cabal's purposes with the apprentices are).
My plan is to play up Sarah's charity virtue, which allows for some interesting conflict between that and the master's goals.