A Bio-Band, known in Japan as a Death-Belt is a device given to the students at Duel Academy by Thelonious Viper to monitor their progress while Dueling. It collects Duel data, fighting spirit, concentration and the decisions of a player. It sends this data to Viper's headquarters. If the result shows that the student doesn't sustain sufficient fighting spirit, he or she will be degraded and finally kicked out of the school. It is later discovered that they absorb the energy of the Duelist while they are Dueling, and the energy is used to resurrect Yubel. The amount of energy drained varies; the Duelists might not even notice it if it's on a low setting but on higher settings it can cause them to collapse from exhaustion or even die. In the English dub, Adrian could have deactivated the Bio-Band's main reactor, rendering them useless but is seduced by a promise of power by Yubel and chose not to shut it down. In the original version, Jesse told Crowler that, aside from cutting off his hand, he couldn't remove the Bio-Band. This is also said by Alexis in Yu-Gi-Oh! GX Tag Force 2. This statement is however left out in the English dub, which causes confusion as to why they didn't just take them off, as the Bio-Bands were the cause of Duel Zombies.