I definitely don't understand Dark Days: The Forge.

Can someone help explain the plot of Dark Days: The Forge to me? I don't understand anything that went on in the issue. I've seen the golden tower before, but I don't remember where and what it does.

Whats all this talk about Metal? Why is Hawkman suddenly involved? Why are the Outsiders back? Why was the Joker locked up? Why is Plastic Man in the cage?