"I don’t think it’s explained very well in the story, but the idea is that scientists and biologists created a giant machine for harvesting natural resources, but it malfunctioned and ended up destroying the local environment by letting anything useful rot and stagnate within its structure. The scientists made underground stations to help maintain whatever plantlife was left from above, using mirrors to get sunlight underground. That’s the backdrop, anyway. The creature/machine was inspired by the giant scrap robot in the eden project, and most of the rest of the comic is inspired by all the people and bits and pieces dotted around the area."
So yeah. That's it!