Dr. Vellian Crowler, known in Japan as Cronos de Medici (クロノス・デ・メディチ), is a fictional character in the anime series Yu-Gi-Oh! GX (Yu-Gi-Oh! Duel Monsters GX in Japan).
35-year old Crowler is a professor at Duel Academia. Crowler secretly tries to force low-performing students out of his school. After the main character, Jaden Yuki (Judai Yuki), defeats Crowler at a duel, Crowler tries as hard as he can to get Jaden out of the Duel Academia.