|Japanese translated||Cronos de Medici|
|Rōmaji||Kuronosu de Medichi|
|Manga debut||Yu-Gi-Oh! GX Chapter 1: "A New Hero!!"|
Vellian Crowler, known as Cronos de Medici (クロノス・デ・メディチ, Kuronosu de Medichi) in the Japanese version, is a character in the Yu-Gi-Oh! GX manga.
Crowler was defeated in a Duel by Jaden Yuki, as part of Jaden's entrance exam. Because of this humiliation and Jaden's academic ineptitude, Crowler harbored a strong distaste for Jaden.
Mr. Ryuga's application to be a teacher at Duel Academy, was overseen by Crowler. This process required Ryuga to win fifty Duels in a row against students. Crowler commended him on winning forty nine and after overhearing Jaden arguing with Ryuga, he suggested that Jaden by Ryuga's final opponent. Ryuga used the technology in his ring to disable Jaden's ability to active Spell Cards. Spectators took note of Jaden's difficulty activating a card, which Crowler blamed on Jaden's negligence in taking care of his equipment. Crowler was annoyed to have been let down by Ryuga when Jaden still managed to win.
Crowler hosted an extracurricular skill lession, where at the suggestion of Chazz Princeton, Chazz Dueled Jaden.
Crowler went to Midori Hibiki's office to get the results of the midterm exam. He found that the office was unlocked but vacant. He then remember that she was away on business that day, but spotted a printed copy of the exam results and noticed a score of 0 for Syrus Truesdale. Unbeknownst to Crowler that was just the first draft of the results and the 0 was a standard procedure for students who leave their name blank. He impulsively took it on himself to expel Syrus. He found Syrus in the video room, where Jaden Yuki, Alexis Rhodes and Bastion Misawa were questioning him about his brother, Zane Truesdale. Crowler interrupted the conversation and asked how it was possible Syrus was related to Zane, one of the academy's finest students. He announced his intentions to expel Syrus, but gave him one chance to cancel the expulsion; he would need to defeat Jaden in a Duel. Due to Jaden's failure to pass a single written exam, Jaden would need to win the Duel or he would have his Deck confiscated. Hibiki arrived just as Jaden won the Duel. She explained that Syrus had really scored a 91, so would not be expelled, and that she would be reporting Crowler's misconduct.
A practical skills class was conducted jointly between Slifer Red, Ra Yellow and Obelisk Blue, with Crowler helping organize it. He announced which Duelists were to face each other, including Jaden Dueling an Obelisk Blue.