Duke is the king of Southtown and the leader of the Mephistopheles gang. The Mephistopheles gang is a subgroup of the underworld organization Addes.
He answered Jivatma, who worked for him before becoming the leader of Mephistopheles. Jivatma called him "D" (although he hates the name) and his subordinates, long, and "N". Currently, Duke is considered a traitor to Addes, although he is a member of the Kokaviel Children's Organization (a supreme authority of Addes). He has contact with Lenneville because he is responsible for the death of his parents, but he is spared. Duke is also responsible for the death of the mentor of Fate, Alba and Soiree, but not directly responsible for himself.
After being defeated by Alba, Duke entered the next tournament to redeem himself, thus losing his status as the king of the South. After his parents disappeared, he apparently underwent surgical revisions at an early stage. He underwent surgery so that Ades could cure his sister and die for an unknown reason. The fact that she passed away greatly plagued Duke, who often issued a statement "This is an old story... 20 years ago."
- His hobby is listening to operas and he is apparently a big dog fan, owning no less than five St. Bernards.