Note: Details on sections of this page will be updated once cards and skills are 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.
When is Vellian Crowler available?
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.
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.
Assuming that Dr. Crowler is the unlockable duelist, which is 100% possible, I would like to see Geartown at the start of the duel as a Skill. What the Field Magic card does is allows both players to Normal Summon an "Ancient Gear" monsters with 1 less tribute. When the card is destroyed and sent to the Graveyard, you can special summon 1 "Ancient Gear" monster from your hand, Deck, or Graveyard. If you have AGG in your starting hand and use Cost Down while Geartown is out, you can summon AGG easily w/o tributes.