- "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 fog[src]
This 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, 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.
The effects of the fog included itchy scabs, convulsions, painful pustules, and rapidly atrophying muscular tissue and sometimes death. Katniss Everdeen recounted that when she was helping Peeta Mellark escape, the fog had reached one side of his face, causing the muscles on that side to collapse, shudder, and die.
Haymitch Abernathy gave Katniss a thick, tar-like ointment to treat her scabs and scars, which she found very soothing although it turned her skin a sickly green color while it healed. Soaking in salt water also relieved the effects of the fog, though this was a very painful process. Using this method required that the affected enter the water bit by bit, or else they risked intense agony.
Mags, the oldest tribute in the 75th Hunger Games, was the only known tribute to die from the fog. As the fog approached, she realized that Peeta would die unless Finnick carried him, and since Finnick was unable to carry both Peeta and Mags, she sacrificed herself. Up until that moment, Finnick had carried her everywhere, but she realized that Peeta would die if they continued with this. She got off Finnick's back, kissed him good-bye, and walked into the fog. Her death was described by Katniss as being like a dance, which demonstrated the fog's power of muscle manipulation. Mags was noted and respected by Katniss Everdeen for her actions. Peeta, Finnick, and Katniss later suffered severe muscle damage by stray droplets of the fog.
- Catching Fire, Chapter 20
- Catching Fire, Chapter 21
- Catching Fire, Chapter 22