With Chancellor Lorak afflicted by a debilitating illness, Kalnor rallied support among the other Great Houses and attempted to overthrow Lorak's regime. In a battle with Lorak's loyalists in orbit of Qo'noS, Kalnor's VoDleH class battlecruiser is crippled by General Chang's command ship, causing damage to the engines and knocking out its shields.
Chang, seeking a quick end to the conflict, ordered his chief engineer to beam him onto Kalnor's bridge, where he challenged the traitor to a blood duel. Kalnor attempted to refuse and offered Chang a place in his future regime; Chang accused him of cowardice, and so the duel was on. Despite being blinded in his left eye by Kalnor's d'k tahg, Chang emerged triumphant, killing Kalnor and ending his attempted coup.
Kalnor was succeeded as head of the House of G'Iogh by his half-brother, Melkor, who would subsequently launch his own bid to control the Empire, albeit as Emperor rather than Chancellor. During the war that followed, Chang commented that as untrustworthy as he was, Kalnor was at least a relatively honorable fighter compared to his brother. (TOS video game: Klingon Academy)