Chi Aques III

A habitable planet of the Chi Aques system.

This planet used to be the homeworld of a previous spacefaring civilization of humans. There are few humans left and their civilization has largely fallen to ruin. This is mostly due to the invention of a self-replicating robot that could perform many roles. These robots have quickly multiplied and a number of them have ended up in the various planetary ecosystems. From there, they created their own ecosystem that could live alongside the organics, soon establishing entire food chains, ect. Rather than 'eating' other machines, the robots would dismantle them for parts. This caused significant disruption to organic ecosystems and in turn the fall of human civilization but the ecosystem established a new status quo. Humans have largely divergently evolved as well, some becoming partly mechanical, or even fully mechanical. They have created a new civilization which is still in its very primitive stages. Rather than thriving, they struggle to survive in these new conditions. 

This has resulted in a very unique ecosystem where machines and organisms interact with each other very often in very organic ways. Both sides have driven the evolution of the other, for example the machines have helped some aquatic organisms to achieve massive sizes. These can grow to lengths of several hundred meters. The machines can edit DNA of organisms much more quickly than evolution, and organisms have found ways to edit the machine's 'genome'. 

There are still ruins around the planet from the previous civilization millions of years ago. These have all decayed immensely now mostly resembling piles of rocks that organisms and organic machines now live in. There is little technology to recover and few signs of what period they might have been, but many items and even people are buried deep underground and recoverable. These should provide signs of the earlier civilization.