Plaon was the lone natural satellite of Janjur Qom, the San'Shyuum homeworld. Old, small, and cratered, the moon cast a silver light on the planet at night. Prior to the firing of the Halo Array—after being exiled to their home system—the San'Shyuum were permitted by the Forerunners to travel to colonies on Plaon, along with the colonies on another planet in the system and its moons. Minerals from Plaon were used to power the "strident shield" of High Charity. Plaon was likely destroyed when the star Janjur Qom orbited allegedly collapsed in on itself.