Organian

The Organians are non-corporeal life forms native to the planet Organia.

In 2267, when war broke out between the Federation and the Klingon Empire, the Enterprise attempted to secure Organia, but the planet was invaded by a Klingon task force led by Commander Kor. The war was ended when the Organians forced both sides to sign the Organian Peace Treaty. (TOS episode: "Errand of Mercy").

In 2269, the Klingons confined the Organians to their planet with a "thought-barrier", thus allowing war to break out between the Federation and Klingons once again. After the Enterprise reached Organia and freed it, the Organians confined the Klingons to their homeworld for 1000 years (TOS novel: Spock Must Die!)

In 2371, as James T. Kirk lay near death on Veridian III, he was revisited by the leaders of Organia, who showed him the difference his decisions made in history. (TOS short story: "Reflections")