It existed far before humanity, was summon by humans who thought they could use it and controll it. Its mind and body altering. invisible and (somewhat) impossible to grasp fully.
That show is so hard to watch from the standpoint of someone who understands what every exposure is doing to people and the awful deaths that are inevitable. Watching the firefighter pick-up a piece of the reactor was horrifying in a way so little horror is.
The moment they look over the railing into the very mouth of God itself gives me chills. The sound of the nuclear fire blasting and spewing out all the smoke and radiation.