The Devil Arm is a mysterious arm that was found by Professor Viper on one of his expeditions. It has the ability to see the dark thoughts of any person's mind. Only those with evil in their hearts may control it. The devil arm is actually the only part of Yubel that wasn't destroyed when she was launched into space by Jaden when he was a child. When Yubel was controlling Marcel Bonaparte, his left arm was covered by this arm. When Yubel was controlling Jesse no such thing happened, this was probably due to the fact that Yubel had her own body.