He's the Duke, and he likes to party.
The Duke has had some form of military training, as obviated by his spotting skills at the end of Diplomacy, and referenced in his conversations with Patches in Be Our Guest. He also mentioned that he had considered returning to that life, but had to stop because Duchess Eloyse was going to mettle in his absence.
Acting as the Duke for the Montreal region, ostensibly under Duchess Eloyse. He holds court at Heart's Light, and otherwise seems to lead a life of leisure.
The Duke's involvement with the Motley has become ever more deep, and he's expressed serious interest in Patches, been kidnapped by vampires, and hidden from the public eye for months. As happens, when you hang around player characters.