One of the luminous globes in which the last survivors of an ancient race, Sargon, Thalassa and Henoch, preserved their consciousness for half a million years beneath a dead planet.
The receptacles are glowing spheres stored in a vault deep under the surface of the lifeless planet Arret. Each contains the pure mental energy of one survivor of a civilisation that destroyed itself roughly five hundred thousand years ago. They appear in the original series episode Return to Tomorrow.
Sargon, his wife Thalassa and his former enemy Henoch ask to borrow the bodies of Kirk, Ann Mulhall and Spock so that they can build android bodies for themselves. While the exchange lasts, the displaced human and Vulcan minds rest in the receptacles.
Henoch means to keep Spock's body. Spock's receptacle is destroyed during the struggle, but his consciousness has been hidden in Christine Chapel. Sargon and Thalassa finally choose to depart into oblivion together rather than live on.