The Klothos was commanded by Kor when he was in charge of the first of two Klingon divisions (the second being commanded by Kang) to participate in an attack against the Federation outpost at Caleb IV, successfully implementing the military stylings of an ancient Earth cavalry attack.
At the time, the cloaking device was a new piece of technology to the Klingons, and Kor was said to have spent three days in the engine room studying the device aboard the Klothos before the mission. (DS9: "Once More Unto the Breach")
Serving under Kor aboard the Klothos in 2269, were his senior officer Kaz, and crewwoman Kali. The Klothos engaged the USS Enterprise in the Delta Triangle region, where the Klothos was pulled into Elysia during the battle, and the Enterprise deliberately followed to escape a Klingon mouse trap maneuver.
The Klothos attempted to attack the Enterprise once again but was intercepted by the Elysian Council, whose laws prohibited violence of any nature. After their encounter with the Elysian Ruling Council, Kor led the Klothos on an unsuccessful attempt to leave Elysia.
|IKS Devisor • IKS Gr'oth • Kang's battle cruiser • IKS Klothos • Kohlar's battle cruiser • Kuri's battle cruiser • L'Rell's battle cruiser • Tal's flagship • Unnamed|
In the 1998 episode "Once More Unto the Breach," an aged Kor said that the Klothos was a D5-class vessel. When the ship was seen in the 1973 episode "The Time Trap", she appeared to be a slight variant of the D7-class. It should be noted that the actual design of the D5-class was not introduced on-screen until the 2002 Star Trek: Enterprise episode "Marauders".
The incident at Caleb IV was not given a date in "Once More Unto the Breach," though it must have occurred at some point before peace was made between the Klingon Empire and United Federation of Planets in 2293. Kor however attributed the swift victory to the fact that Federation did not yet know Klingon ships to possess cloaking technology. It therefore probably occurred prior to "The Time Trap", possibly during the Federation-Klingon War of 2256-57, as depicted in the first season of Star Trek: Discovery.
The Star Trek Online expansion "Agents of Yesterday" establishes that the D5 class underwent a substantial refit in the early 23rd century, resulting in a design very similar in appearance to the D7. This would explain why the Klothos does not resemble the design seen in Star Trek: Enterprise.