Gamma Trianguli VI was the inhabited sixth planet orbiting the primary Gamma Trianguli, in the Gamma Trianguli sector. This was the homeworld of the Vaalians, a pre-warp humanoid species. This was, also, the home of the pod plants. Vaal, a computer-machine with rudimentary intelligence, controlled this planet and its inhabitants for approximately ten thousand years until 2267. (TOS: "The Apple"; Star Trek VI: The Undiscovered Country, okudagram; ENT: "In a Mirror, Darkly, Part II", display graphic)
The planet, described as an "Eden"-like paradise, consistently enjoyed a tropical climate of 76 °F, with only minor variation at the poles. These conditions were previously thought to be impossible, and were only made possible under the direct environmental control of Vaal, which extended deep beneath the planet's surface over the entire globe. The atmosphere was oxygen-nitrogen. The majority of the flora was very attractive. The soil was remarkably rich and fertile, excellent for husbandry. Its atmosphere filtered out all harmful radiation from its sun. Aside from the natives, no animal life was encountered by initial surveys. Vaal was obviously constructed on Gamma Trianguli VI by a species to care for the native inhabitants for some unknown purpose, although the natives had no memory or historical record of this.
Although an Eden at first glance, under Vaal's control the planet soon proved to be the opposite. When a USS Enterprise landing party beamed down on a survey mission, they were immediately assaulted by the planet's dangerous defense mechanisms. Deadly flora, artificial lightning strikes, and explosive mineral formations killed three crewmembers and injured a fourth. The initially friendly natives, at Vaal's behest, also became hostile and assaulted the landing party, killing a fourth crewmember. Vaal itself also began pulling the Enterprise out of orbit, prompting Captain James T. Kirk to take retaliatory action and destroy Vaal. After its destruction Kirk predicted a hard time for the natives, but eventually they would learn to organize their lives themselves. (TOS: "The Apple")
In 2328, this was the point of embarkation for several individuals. Zayra Cabot traveled to Tarsus IV on the SS Manoa, Eric Bruno and Douglas Drexler traveled to Gothos Space Center on the SS Kogin, Jack Litchfeld traveled to Tarsus IV on the Kogin, Daryl Baskin traveled to Gothos Space Center on the SS Wisconsin, and David Stipes and Lorine Mendell traveled to Tarsus IV on the Wisconsin. (TNG-R: "Inheritance", okudagram)
In the TOS-VOY crossover novel No Time Like the Past, Kirk and a space and temporally-displaced Seven of Nine visit this planet to find one of four pieces of an artifact. Seven is transported by the piece she already possesses to the planet's past, not long after Vaal has been put into operation.