This is what I refer as a 3D sketch. I often do these on my iPad, using Nomad Sculpt. Once I have the idea nailed down, I can move the project into Blender to clean up assets, adjust scale, etc. For this particular project, I wanted to create an environment that was somewhat "steampunk". I also had this idea of having humans be dependant slaves to a machine, with the twist being that that the machine itself was a slave.