Legend of Kahless

     The legendary first emperor of the Klingon Empire, Kahless not only united his people some 1,500 years ago but set the standard for the conduct of honor and strength all Klingons live by today. All Klingon children learn the tales of Kahless and his brother Morath, who fought for 12 days and 12 nights because Morath had broken his word and dishonored his family, killing their father. According to legend, Morath then threw their father's sword into the sea to prevent Kahless from having it, but he held his breath for three days and found it. As an adult, Kahless forged the first bat'leth and founded the Empire after slaying the tyrant Molor —a battle celebrated with the Kot'baval festival — and conquering the Fek'Ihri.

     Legend also tells of many other exploits: how he once fought off an entire army by himself at Three Turn Bridge, skinned the serpent of Xol, and carved a statue for his beloved Lukara. As his first wife, they had met after fending off 500 warriors at the Great Hall at Qam-Chee when the city garrison fled. Their vows in that incident are one of the most romantic Klingon rituals of mating ever, often recreated by modern couples. After delivering the laws of honor in later life, Kahless went to the edge of his city and made 'The Promise' to his weeping people that he was leaving to guard the afterlife of the honored dead in Sto-Vo-Kor but would return someday. On the planet he pointed out that night, Boreth, a caste of clerics sprang up to await the day he would return. Only they knew how he created the first bat'leth from a lock of hair thrust into Mount Kristak a tale intended to verify his identify upon return, as it did when a clone of Kahless, taken from blood on the Knife of Kirom, was created and allowed to serve as perfunctory emperor and spiritual guide in 2369.

Reference: Rightful Heir

  The story of Kahless is a cornerstone of Klingon mythology and religion.  According to legend the messianic Kahless fought the tyrant Molor, whom he killed with the first bat'telh or sword of honor.  Another of the epic tales of Kahless relates how he fought his brother, Morath, for twelve days and twelve nights because Morath had lied and brought shame to his family ("New Ground" [TNG]).  Klingons believe that warriors who die honorably join Kahless, who awaits them in Sto-Vo-Kor, the afterlife.  Just before his death, Kahless pointed to a star and promised that he would one day return there.  Klingon clerics established a monastery on Boreth, a planet orbiting that star, where they waited for centuries for Kahless to return.