You must be able to speak or pronounce French.

Duke is a Nevermore student as well as Lenore's closest friend. He's generally a pretty laid-back person that likes to bend and ignore the rules. He also knows some magic tricks and is very skillful in lockpicking.

Duke has a very performative personality, likely due to the fact he used to be a performer. He has a habit of teasing his friends and taunting those on Annabel Lee's side. Despite his constant jabbing, he does care about his friends, seen by how he is a constant form of support for Lenore and even attempted to cheer up Morella by showing her a coin trick.

Despite his feelings towards his friends, and how he's often a very determined, self-assured, and confident person, he seems to not care for himself as much as he does others. When in Dreamland with Lenore, rather then attempting to fight for his life or come up with solutions to his problem, he accepts his fate surprisingly quickly.

I imagine his voice to be fun in sound with a flair of dramatics and a french accent.