B'Elanna Torres grew up on Kessik IV, where she and her mother Miral were the only Klingons. (VOY: "Faces") Aware of this fact, Kohlar, took that into account while interpreting a prophecy that was "written that the mother of the Kuvah'magh would be an off-worlder," but Torres rebuffed his insinuation, indicating that "a lot of Klingons are born off-world." (VOY: "Prophecy")
This planet was only mentioned in dialogue.
Kessik IV was also mentioned in a deleted scene, from "Workforce, Part II", where it was remembered by the amnesic B'Elanna, who described it as the last place she remembered being, "pregnant, scared and alone", prior to arriving at her job on Quarra.
According to Star Trek: Star Charts (p. 64; "United Federation of Planets I") and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), the Kessik system was located in the Beta Quadrant. The system's primary was a G-class star. This system was a vertex of the Delta Triangle. In 2378, the planets Kessik III and Kessik IV were listed as Federation members.
Kessik IV also used to be featured in Star Trek Online until it was renamed to "Omicron Kappa II".