Xi Xiao Jian was a muscular warrior who worked in the Avatar Taskforce. As a child Xiao had exhibited strange traits when he attempted to learn Firebending, having extreme trouble with even the most simple of Firebending techniques. However, he later discovered an almost instinctual capacity for the far more difficult and deadly technique of generating lightning, and honed this technique. Whilst unable to control the lightning to any level comparable to regular bending, Xiao was able to generate lightning faster, more often and with more guidance than any of the other few Benders versed in generating lightning, and thus became known as the Lightningbender. His lethal lightning generating style combined with his heavily muscled frame resulted in a need for an entirely different type of martial arts than that used by regular Firebenders. To this end, he learned the highly explosive art of Bajiquan, meaning Eight Extreme Fists. Reliant on sharp attacks and strikes that release energy explosively as opposed to the momentum-generating moves most Benders used, Xiao's Bajiquan form was his only combat capability in situations where the certain lethality of lightning was undesired.
Xi Xiao Jian had a good-natured personality, but often felt shamed and humbled at the fact that he could not perform even the most basic of Firebending. He sometimes commented on the fact that his only bending skills were entirely lethal and unable to be regulated or even controlled as being a curse and a joke of the Spirit World at his expense. In the post-war peacetime that existed during his lifetime Xiao grappled with feelings of uselessness and displacement, as he was a relic more appropriate for any time in the previous century of war. However, he drew some measure of satisfaction and purpose from his artistic skills, which he believed were unrivaled within the Worldbender organization.