Steel city
After going on a rampage showing off his power at the bank and bringing down the weaker Epic, Steelheart goes on to turn the entire city of Newcago into steel. There are a lot of images of objects and places which turned into steel, like street lamps that don't give out any light, parks with grass that has turned into steel, and the most interesting, emotionally disturbing as well, is the image of David's father whose body got turned into steel after he died, making it appear like a statue from that time.
Tunnels
Our protagonists have to go through a lot of underground tunnels, which is given considering the nature of their job, which requires them to be secretive and stay hidden. A lot of the tunnels are left naturally in the underground after the Diggers (who eventually turned crazy from the work they had to do and their work started to take on a peculiar appearance) stopped with their work. Most of them are made on the spot with the special equipment provided by Prof called the tensors, which are used to destroy steel. This is how the Reckoners were able to complete the most impossible missions-because they were able to get through places no one else could.
Calamity
Calamity is a star, or a comet-it is not precisely cleared out-that appeared shortly before Epics started to appear. It is believed to be the cause of them. The answer to how it suddenly appeared or where it came from is left unexplained. The only thing that is clear is the ominous nature of the phenomenon, especially combined with the never-ending darkness, which makes it look like a watching red eye on the sky.
