Eternal One (The Moon Era)

The Eternal Ones are a sapient species of hostile cyborgs derived from members of the Mother race which fused themselves with technology to become a new species. They inhabited the Earth's moon Luna billions of years in the past, when Luna was an Earth-like temperate world and not yet tidally-locked.

Biology
The Eternal Ones are biomechanical creatures. Their sole organic components consist of grey masses of neural tissue with a pair of eyes and a number of feeble tentacles. Their atrophied bodies are encased within a robotic exoskeleton that gives them movement and strength. Their name derives from the fact that they use technology to greatly extend their lifespans. Even so, they are not actually immortal. At some point, their brains cease to function with age and rot away inside the machinery.

Since the Eternal Ones split from the Mother species, it can be inferred that they too are probably all female. However, they cannot reproduce and their only way to increase their numbers is to forcefully convert new Mothers into Eternal Ones. After the Mothers became extinct, the Eternal Ones presumably died out as well.

Culture and society
Their technology includes teleportation devices. Despite their advanced technology, they never developed the means to explore space beyond their homeworld.

Appearances

 * "The Moon Era", by Jack Williamson (1932)