The Celestials lived a harmonious life in their utopia. But this peace was interrupted by an attack from the great monster Orochi and his large army of demons. Waka of the Moon Tribe tried to help the Celestials escape by boarding them onto the Ark of Yamato. However, all the Celestials were later killed by the great evil lurking in the depths of the Ark--the Dark Lord Yami and his endless legions of demons. Waka was the only survivor of this genocide.
The spirits of four Celestials managed to survive on the ark and told Amaterasu about the events that had led to the ark crashing. They faded away one by one and passed on, removing the last trace of Celestials from the universe.