The Story of the Promise is a belief among the Klingon people that originates from Kahless the Unforgettable.

The story explains that Kahless told the Klingon people that he would be journeying to Sto-Vo-Kor but made a promise that he would return one day, at which he pointed to a star in the sky and told the people that search for him at that location.

When the Klingon Empire expanded into space, they established a colony on the planet Boreth which was believed to be the site where Kahless will make his return.

(TNG episode: "Rightful Heir")