This is the cornucopia where all the tributes start the games and run to the middle to collect all the resources and weapons. The Cornucopia is designed like a clock and it is located in the center of the designated area of the games. Cornucopia is a dangerous place to be a lot of people die there to try to get weapons but you have a choice to either go and grab weapons or run away and try to find resources somewhere else. Katniss and Peeta had there own plan to run to the middle grab their weapon of choice and ran away
It continues to approach at a steady pace. Tendrils reach forward and then curl like fingers, as if they are pulling the rest behind them. As I watch, I feel the hairs on my neck begin to rise. Something's wrong with this fog. The progression of the front line is too uniform to be natural.―Description of the poisonous fogThe fog in Catching FireThis type of fog was a poisonous, corrosive vapor released by the Gamemakers in the 75th Hunger Games arena as one of the hourly horrors. It came between two and three and spread throughout the jungle. It resembled an after-rain fog, had a sickeningly sweet odor and advanced in a straight line,[1] growing and becoming thick and acrid. It killed muscles, made its victims twitch, and could lead to death. The fog was made by the Gamemakers of the third Quarter Quell.[2]
The Lighting strike was another event in the games. At first, everyone thought it was just a storm coming in. We see the tree get struck and a tribute but then Beetee was saying 'Tic TOk' over and over and everyone thought she was in shock. Katniss realizes that the lighting strikes every 12 hours at the designated spots. Katniss realizes that the lighting was going through the force field. She wraps the wire around one of her own arrows and Finnick finds her and starts telling her to back away from the tree (because it's almost midnight). Instead, she shoots it into the force field which breaks it and removes all the power from the arena.