Melkor, son of G'Iogh was the head of the House of G'Iogh after the death of his half-brother Kalnor in his coup attempt against Chancellor Lorak in 2291. Melkor's ancestry could be traced back to the Emperor Sompek.
Despite Kalnor's treason and death, the House of G'Iogh had lost little of its influence and power. Sometime late in 2291, Melkor - deciding to wait until after Lorak succumbed to his illness to make his move - met with the heads of four other Great Houses to discuss his plans to take control of the Klingon Empire. General Chang, who slew Kalnor in single combat earlier that year, dispatched his best student from the Elite Command Academy, Torlek, son of Ro'vagh, to spy on Melkor's meetings, sending back vital intelligence. Shortly after the Academy class of that term graduated, Lorak finally died...but rather than stake claim on the Chancellorship, Melkor declared himself Emperor of the Klingon Empire, a post that had been vacant for centuries. The result was civil war, with the Empire being divided between Gorkon, son of Toq, the legitimate successor to Lorak; Chang, opposing both Melkor's power-grab and Gorkon's ascension, as he condemned Gorkon's plan to make peace with the United Federation of Planets; and lastly Melkor himself, known to the other factions as the Usurper.
The early stages of the war were fought largely between Chang's smaller faction and the House of G'Iogh, with the Usurper gaining ground via sabotage and treachery. But he made a fatal mistake when, instead of allowing the Tal'Ihnor Gates to fall to Chang's forces, Melkor completely obliterated the system by causing the Tal'Ihnor sun to go supernova, destroying the Empire's key energy production center (forcing the overmining of Praxis that would lead to disaster not long after) and costing Melkor all support he had in the Empire. But Melkor, much like the House of Duras seventy-five years later, called on outside assistance - the Romulan Star Empire - to continue his bid for the Emperor's crown. Luring Chang into an ambush in an effort to destroy him, Melkor was driven off with the aid of Torlek, who had turned to Gorkon for support. This infuriated Chang, as not only had the Usurper escaped, but now he was indebted to Gorkon - which meant that he would be forced to allow Gorkon to formally ascend to the Chancellorship.
With the Romulan fleet at his disposal, Melkor made one last desperate bid for power. After a deception that lured Chang and the bulk of the Klingon fleet to the Federation Neutral Zone, fooling them with a fake distress call into believing an invasion was imminent, Melkor led a large Romulan fleet in an assault on Qo'noS itself. Gorkon, trapped on Qo'noS, sent Captain Torlek to convince Chang to return to defend the Klingon Empire from the Usurper's mad scheme. Leading the fleets in, Torlek engaged the Usurper's flagship, the QeylIS BetleH class IKS wo'HubwI', and destroyed it, killing Melkor and ending his bid for power.
With Melkor dead, his forces in tatters and the Empire left on the brink of disaster, the House of G'Iogh suffered discommendation by the Klingon High Council, and those who fled to Romulan space were hunted down and destroyed by the Klingon fleet. (TOS video game: Klingon Academy)