The Underground Dueling bar was a a drinking establishment, which housed Underground Dueling in the Yu-Gi-Oh! GX anime. Zane Truesdale Dueled Mad Dog here when he begun Dueling under Mr. Shroud's management.
The bar is located in a run down part of a city. Its interior is dimly lit, with the exception of a cage, in which Dueling takes place. The spectators sit at tables around the cage and usually wear domino masks. The Duelists each wear a set of electrodes, which deliver electric shocks as they lose Life Points. Duelists are not allowed to leave the cage until after the Duel.
Zane Truesdale's Duelist career hit a low point, after losing at least eleven Duels in a row and being relegated to a minor league. He then contacted Mr. Shroud, who had previously offered to manage him in Underground Dueling. Zane accepted his offer and Shroud arranged for Zane to Duel Mad Dog in the bar. Zane was initially unaware of the conditions of the Duel and felt he had been deceived by Shroud after the Duel began. Unwilling to lose again, Zane took on a more ruthless Dueling strategy and darker persona. He then overpowered Mad Dog, winning the Duel and ending his losing streak.
- Yu-Gi-Oh! GX episode 65: "No Pain, No Game"