Kloog was a large, dark-skinned humanoid with fangs and bushy eyebrows who was held captive on the planet Triskelion, where he served as a thrall.
He was killed by Captain Kirk when the two fought each other in 2268 in order for him to reunite with his crew. (TOS: "The Gamesters of Triskelion")
Kloog was played by actor Mickey Morton.
According to the first draft of the episode, still entitled "The Gamesters of Pentathlon", this character was named 'Klong'.