There are multiple story ideas from Star Trek: Deep Space Nine's hypothetical season 8 that can be made canon in the wider Star Trek universe. DS9 season 8 was conceived as part of the retrospective documentary What We Left Behind – Looking Back at Star Trek: Deep Space Nine. The documentary reunited showrunner Ira Steven Behr with writers Ronald D. Moore, Robert Hewitt Wolfe, René Echevarria, and Hans Beimler to "break" the story for a possible reunion series. As well as providing insight into where the writers saw DS9's characters in the years since the series ended, it also provided a demonstration of how their writers' room worked back in the day.
The overall storyline of Star Trek: Deep Space Nine season 8 centered around a Section 31 plot to destroy the Celestial Temple. This plot to remove religion from the Star Trek universe would have pitted old friends against each other, building to the heroic return of the Bajoran Emissary, Captain Benjamin Sisko (Avery Brooks). As an outline for a DS9 revival season in Star Trek's future, it's a strong concept, and here's every element of the storyline that should be officially canonized.
