The beginning.
During the 2030 technology boom, companies continued to consume and capitalize everything. Life was commodified and everything started to decay and be destroyed slowly. Day by day the environment decayed and life faded away, in 2056 a group of unknown individuals gathered together to try retain humanity. Their goal was to develop a robot that the coined a Syphobot. A robot type powered by AI and electricity, though it simulates emotions and thought very well. The main part that was difficult was finding a method to to be able to transfer the human consciousness.
After lots of effort by 2063 the technology was complete and the process of creating what is known as "The first wave" of Syphobots begain. Human minds and knowledge where transferred into bodies that could better survive the growing wasteland earth was becoming. They spent alot of resources excavating caverns to house the Syphobots in a relatively safe enviroment. They built housing and buildings hanging from the ceiling connected by bridges, From there they had to build and sort out the stuff for themselves. They abandoned the surface and cut off contact with some of the remaining civilizations.
They developed the caverns themselves using materials harvested from the caves. They expanded the city, built and managed stores and hosted public events. It was only 40 years until them managed to build a massive underground system the size of europe and social systems and ways of creating more bots. States, goverments and societies were created and formed around the underground world.
Syphobots mine lots of valuable and important minerals as well as doing jobs to keep everything running smoothly and nicely. Sometimes weapons developed and are made to be able to fit within their shell and be extracted when necessary. But they are mostly uncommon and never get used, commonly getting removed willingly due to comfort reasons.
The surface world is mostly bland and empty, most of the surface is desert and a harsh one at that. Completely inhospitible to humans, its said that the remaining surface humans escaped to space but no knowledge is properly known about that.