Fog of Lost Souls

The Fog of Lost Souls is a prison for humans inside the spirit world. Inside there are no walls, but there is an unescapable fog which is actually a spirit, slowly causing all of the humans inside it to go insane.

History
In 99 ASC, La took Zhao out of the physical world and brought him here, as a punishment for attempting to kill The moon spirit. He spent eternity here, continuously searching for Avatar Aang, after the fog spirit drove him insane.

Seventy-two years later, Jinora was brought to the Fog of Lost Souls after being captured by Unalaq during his attempts to open the Northern Spirit Portal. She spent approximately a week there, until Tenzin Bumi and Kya arrived. They were sent to the prison by a spider spirit, and searched the location for Jinora. They bumped into Zhao, who mistook Tenzin for Aang. Slowly, however, Kya and Bumi were affected by the fog spirit and began to go insane.

Tenzin attempted to stay calm, but was confronted repeatedly by his expectations to be just like his father. After an image of his father appeared to him, telling Tenzin that he was not, in fact, like his father, but like himself. Tenzin's mind began to clear out, and the fog spirit left the premises temporarily. Tenzin found Jinora, Kya and Bumi, and evacuated the prison just before the fog settled back in.