L'Kor was a Klingon warrior who was a member of the garrison that defended the Khitomer outpost in 2346. He was a friend of Mogh, and even went hunting with him and his son, Worf. Charged with defending an outpost on the perimeter of Klingon space, L'Kor, along with some other Klingons, was rendered unconscious and taken prisoner when a Romulan vessel attacked Khitomer. When L'Kor awoke, he was interrogated for three months. During this time, he attempted to starve himself to death, but was kept alive in a desperate condition by his Romulan captors.
When the interrogation was over, the Romulans were prepared to return the Klingons in exchange for territorial concessions. The Klingon High Council refused, due to the dishonor this would bring. The Klingons themselves refused to return for fear of bringing dishonor on their families.
The Klingons were transferred to a compound on Carraya IV where the Romulan commander took pity on them and allowed the group to stay at the compound and in time they lived peacefully with their Romulan captors, with L'Kor as their leader. L'Kor also shared leadership and administrative duties with the Romulan commander as the two are seen working together.
When the peace was shattered by the arrival of Worf in 2369, L'Kor initially tried to hold him against his will at the compound. L'Kor still refused to return home, claiming it would bring dishonour on his family if he were known to be alive. As Worf began to teach the young Klingons in the compound about their culture, he was allowed him to bring one of them, Toq, on a ritual hunt. When some of the young people decided they wanted to leave, L'Kor eventually stood up for them against the Romulan jailer, Tokath. He, however, remained in the colony. (TNG: "Birthright, Part I", "Birthright, Part II")