Let's Make A Deal.

He's the head of a weapons company inherited from his father; however, a lot of his business is pretty shady and kept quiet. He has connections and supplies and information and he is more than willing to share, for the right price. If you can’t pay him back, though—or if he suddenly decides to collect early—he has the right to do what he wants with you because you entered that contract with him.

And for his personality aside manipulative/persuasive thing you’d expect from his work he's got a pretty violent temper; he’ll hold it in as long as he can but it tends to be pretty obvious when he’s starting to get to his breaking point, his hands might shake or there’s something about his face or he might break something he’s holding (like a drink glass). He loves to humiliate people and have power over them, and he loves to spoil himself (and his bodyguard coughonlyfriend) mostly by buying extravagant things.

He and Allan had a bit of an exchange for a while; Allan would do work for him, and Marquis would supply him with hardware/software/whatever he needs. Allan asked for a little too much pretty frequently (and Marquis pulled some underhanded things to trick him), so he was trapped for a while.