Karden was a Kazon-Ogla youth who initially had the name Kar prior to his efforts to earn his warrior name. He had at least one brother, Jal Kinell, who had been killed in battle.
In 2372, he encountered Commander Chakotay when Chakotay's shuttle drifted into Kazon space. Chakotay was fired upon by Kar, who had to kill the Starfleet officer in order to earn warrior status. Unfortunately for him, Chakotay destroyed Kar's shuttle, but beamed him aboard before it exploded.
When Chakotay returned Kar to his people, he was imprisoned along with Kar. Kar was disgraced and sentenced to death by the Kazon leader Razik. Razik told Chakotay he could go free, if he killed Kar. Chakotay overpowered Razik and escaped with Kar. The two landed on the Kazon moon Tarok, which was used as a training camp. Razik and the Kazon found them, but Kar killed Razik, proclaiming that Razik was his enemy, not Chakotay. Razik's second in command, Haliz, became the new First Maje, and he pronounced Kar a warrior and gave him his warrior name, Jal Karden. Chakotay was freed, but Karden told Chakotay that the next time they met, he wouldn't hesitate to kill him. Chakotay, back on Voyager, finished the ceremony Kar had interrupted and prayed to his father to watch over the youth, saying that he had a difficult path to travel. (VOY: "Initiations")
Karden was played by actor Aron Eisenberg, who played Nog on Star Trek: Deep Space Nine.
According to the script notes, Kar was described as "a young boy who looks to be no older than twelve or thirteen, barely on the brink of adolescence."