The Lake of Lusor was a lake located on Qo'noS, the Klingon homeworld, near the Kri'stak volcano. According to Klingon religion, after plunging a lock of his hair into a river of lava from the volcano's summit, Kahless the Unforgettable forged the Sword of Kahless, the first bat'leth, by cooling and twisting the sword in the Lake of Lusor. (TNG: "Rightful Heir" )