What's Known[]
The Robot Builders also known as Masters were a technologically advanced extraterrestrial species, and the creators of the Robots. They are known to have built Rings on two planets, the Amber planet and the Water planet. It is believed the species were very much akin to their creations, as it is said the Robots were created in their own image. They were briefly mentioned by Will Robinson (Netflix) in the episode Precipice.
The Alien City[]
On The New Guy, Will Robinson finds skeletal remains of The Robot Builders in the alien city and finds the likely source of the robots programming and language through sounds on the cities control panel.
The Robot Builders Fate[]
The Robot Builders were revealed to be exterminated by SAR, one of their own creations in Final Transmission. During Trust, Will Robinson alludes to their death being by the Alien Engine being detonated on the Shattered Planet, causing a large part of the planet to be torn off into orbit. It is also likely this explosion was the cause of the lack of atmosphere on the planet. The detonation caused the extinction of The Robot Builders.
Appearance[]
Not the full appearance was revealed in Season 3 but what's known is the skeletons in the Alien City their appearance is basically organic versions of the four armed Robots and could possibly be also organic versions of the two armed Robots.
Based on the design of the Robots their skin could have been Grey, Blue or Black. Or, in the unique case of Scarecrow and the big silver robot, Goldish Copper (non- oxidized) and Silver.