However, despite his unique ability, Xu was defeated and killed by Kyoshi when she entered the Avatar State. Xu surprised her by attacking her with lightning, which she was only able to survive due to the chainmail in her dress grounding the lightning. In 296 BG, Xu's surviving followers freed him, but he was challenged to a duel by Avatar Kyoshi.
Upon being defeated by Jianzhu, he was imprisoned to be studied by Jianzhu's allies in the Fire Nation so they may learn how he was able to bend lightning. At that time, the last known practitioner of the art was Xu Ping An, the outlaw and insurgent leader of the Yellow Neck uprising, who had used his rare abilities to gather a large army and devastate the Earth Kingdom. By the 4th century BG, most people believed lightning generation to be mere folklore or something lost to history, though Avatar Kyoshi's firebending teacher Rangi stated in 296 BG that there were a few elderly people living in the Fire Nation who had witnessed it. For centuries, the skill of lightning generation was so rare that few even knew that it was possible at all.
