Note: This page will be updated once Vellian Crowler in Duel Links is officialy confirmed.
Vellian Crowler is the head professor and department chair of techniques at duel academy. Initially started out as the antagonist of the show, Crowler wanted to expel Jaden from the academy, attempting several times. After losing the duel against Jaden, Crowler eventually had a change of heart, becoming more of a respectable teacher, as well as serving as a comedic relief.
At the 30 seconds mark of the Yu-Gi-Oh GX Duel Links video, we can see Vellian Crowler at the left side drawing his signature card Ancient Gear Golem. In the recent update provided by Konami this September 25, it says that we can obtain a new legendary duelist in GX world this late October. Based on the manner of speech written on the text, there's a high chance that it is Vellian Crowler.
Vellian Crowler leak
Vellian Crowler character profile in Duel Links has been leaked by XOF the dataminer. Here is the leaked image.
Using the Ancient Gear archetype, which are mostly Machine-Type monsters, Crowler's playstyle revolves around trying to summon gear golem as soon as possible. This allows him to attack without without getting stopped by spell/trap cards, and difficult to go against since it also inflicts pierce damage.