The Galateans were a race of robots.
At one time the human race was dying of a plague. Their solution was to create bodies for themselves that would be resistant to the plague. Keltor Jacobs created the Galateans and the humans uploaded copies of their minds into them. They were placed on the Moon until their activation. Three hours after their activation, the humans discovered a cure for the plague, but it was too late. The Galateans had rebelled and began attacking the humans. Keltor was about to use an electromagnetic pulse to disable them, but before he could, he was killed by Chiyoko so she could assure her creation.
The result was a war between the humans and Galateans which lasted for thousands of years. The Galateans and humans both worshipped Chiyoko as a god. Near the end of the war, before the destruction of Earth, Chiyoko decided that the Galateans were superior and that the humans would have to "go away".