Margon zantai-Demma was a Klingon man of the line of Demma and a General in the Klingon Marines in the 23rd century.
Circa reference stardate 1/65 (circa 2230), Margon held the rank of sutai of the Demma line. He officiated at a game of klin zha kinta played between Force Leader Mabli vestai-Galann and Thought Admiral Kethas epetai-Khemara, during which tossed spindles to determine who would go first. When Mabli's cheating during the match was exposed, Margon killed him for it.
Margon claimed to deny the existence of the komerex zha - the Perpetual Game. Nevertheless, prior to the match, he had caused Vrenn to be labeled as being of the line of Rustazh, such that Kethas would adopt the son of his old friend, Kovar sutai-Rustazh. Thus, Margon and his allies could use Vrenn against Kethas.
By circa stardate 1/78 (circa 2238), Margon had risen to zantai of the line Demma. He had Merzhan use the revelation of Vrenn's heritage against Vrenn, now Krenn sutai-Rustazh.
Margon was marked by a scar at the side of his mouth and a generally unpleasant appearance. He had a female kuve consort with retractable claws. (TOS novel: The Final Reflection)