Kasiel was a Klingon male who served as the Klingon Empire's Ambassador to the United Federation of Planets circa 2300. In the years immediately prior to the signing of the Khitomer Accords Kasiel served as an officer in the Klingon Defense Force under General Chang. Following the exposure of the conspiracy of Federation, Romulans, and Klingons opposed to peace between the Empire and the Federation Kasiel's service with Chang was carefully scrutinized. Kasiel was exonerated of any involvement in the plot, but his proximity to Chang meant that he was forced to become the ambassador to the Federation as a form of exile.