Ch'gran was a great Klingon warrior who lived approximately a thousand years ago. In the wake of the Hur'q invasion and looting of Qo'noS, Ch'gran rose to prominence by urging the Klingon people to take to the stars and conquer all threats before they suffered another invasion. Using captured Hur'q facilities and technology, Ch'gran oversaw the construction of a fleet of mighty warships, numbering seven in total, and on the anniversary of the Hur'q invasion, Ch'gran and the fleet ventured forth into space. The fleet later sent word that they had located a world on which to plant their flag, but were never heard from again.
The mystery surrounding Ch'gran's fate, and that of his fleet, was later solved when, during the 2290s, one of Ch'gran's ships was found adrift in the Betreka Nebula, and again in 2328, which was found by the Cardassians on Raknal V. When the Cardassians refused to surrender the derelict, the Klingons led multiple incursions into the Raknal system, starting the long-remembered Betreka Nebula Incident.
Klingon Imperial Intelligence discovered information on the ship found in the Betreka Nebula that revealed the fleet's fate: Ch'gran's real intention for his fleet, was not to provide security for the Klingon people's future by conquering other worlds, but instead conquer them for himself; after building a larger fighting force, Ch'gran intended to return to the homeworld and take control, putting himself at the top of a new Klingon Empire. Ch'gran's subordinate Captains, not wanting a dictator in power, mutinied and rebelled to stop Ch'gran; the ships in the fleet destroyed each other, killing Ch'gran and ending the threat he posed.
The Intelligence official who discovered the information, a descendant of Ch'gran's House, sealed the information, but was nevertheless revealed to certain members of the nobility, including Chancellor K'mpec, who officially changed the Empire's position on the Raknal V wreckage due to the possible information it contained, ending the Incident. To preserve the memory of Ch'gran as a noble warrior, the entire affair was kept secret from the general Klingon population. (ST - The Lost Era novel: The Art of the Impossible)