The O'karess system was a restricted star system in Klingon space. It possessed a main sequence star and four planets, one of which was a J-class gas giant, with an L-class moon, Pa'thor.
Approximately two weeks after departing Starbase 24 on her way to Narendra Station, the USS Ross received a distress call from Pa'thor, and diverted to the O'karess system to investigate. ("Before Hell pt. 1")