Although they work for a designated employer, it is not clearly defined who the leader of the Card Professors is, but the strongest duelist amongst them has the privilege of using the Black Duel Disk. This special Duel Disk has anti-cheating detection software built-in to the hardware that will set off an alarm if the user attempts to break the rules while using it. This specialized piece of equipment was initially used by Richie Merced, but he was defeated by Keith Howard and forced to surrender the Duel Disk to him. During the rematch duel with Joey Wheeler, Keith lost a second time and gave it to him. At the end of the manga, Joey passes it down to Tilla Mook in repayment for her having previously lent Joey her Duel Disk.