Three Clans; EarthClan, SunClan, and MoonClan, have descended from the legendary SkyClan of myth. Together they are known as the Celestial Clans, and their destinies are bound together by their shared faith in the ancestors of StarClan, who are a constant presence in all of their lives. The ghostly figures communicate with the living through crystal clusters scattered around the territories, guiding and helping the three clans to survive. 

But something's not right in the heavenly realm, and the Medicine Cats have sensed an impending doom....