Camus II was the inhabited second planet in its star system. This ringed world was the homeworld of an extinct alien civilization. At that time, visitors had to avoid exposure to celebium, which was deadly to humanoid life, by using celebium shielding. Archaeological excavations by Humans of the ruins began in the mid-23rd century.
In 2267, Doctor Janice Lester was sent to Camus II with a team of archaeologists to investigate the planet. When Dr. Lester found a life-entity transfer machine built by the now extinct Camus II natives, she devised a plan to take over the body of James T. Kirk and assume command of the starship USS Enterprise. Two years later, together with Dr. Arthur Coleman, Dr. Lester, secretly murdered the entire expedition staff by radiation exposure to lure the USS Enterprise to the planet to investigate the "mysterious" deaths. (TOS: "Turnabout Intruder")
In 2293, the location of Camus II in the Milky Way Galaxy was labeled in a star chart that was in Captain James T. Kirk's quarters aboard the USS Enterprise-A. (Star Trek VI: The Undiscovered Country, okudagram)
In 2328, this was the point of embarkation for passengers traveling to Deneb II City via commercial transport. Rene Echevarria traveled there on the SS Manoa, Molly Amos traveled on the SS Kogin, and Wendy Knoller and Eric Alba traveled on the SS Wisconsin. (TNG-R: "Inheritance", okudagram)
According to the Star Trek Encyclopedia (4th ed., vol. 1, p. 115), Camus II was referred to in "Legacy", the 80th episode of TNG, as a homage to "Turnabout Intruder", the 79th and last episode of TOS. The "in-joke" was devised by Rick Berman, Jonathan Frakes and Eric Stillwell.
According to the Star Trek: Star Charts ("United Federation of Planets III") and the Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), the Camus system was located in the Alpha Quadrant. The primary was an M-class star.
According the novelization of DS9: "The Search, Part I" and DS9: "The Search, Part II", if Deep Space 9 was ever attacked by the Jem'Hadar, civilians and non-essential personnel of the station would be evacuated to Camus II. The novelization also mentions that Camus II was known for a particular type of coffee.
According to Decipher's Worlds sourcebook, Camus II is the second planet in the Alpha Camus system. It was once inhabited by a race called the Yiterans.