The Klingon First Empire was forged by Kahless the Unforgettable, after his defeat of the tyrant Molor and the Fek'Ihri. (DS9: "The Sword of Kahless")
It was presumably succeeded by the Klingon Second Empire.
The Klingon First Empire was forged by Kahless the Unforgettable, after his defeat of the tyrant Molor and the Fek'Ihri. (DS9: "The Sword of Kahless")