This is considered to be one of the darkest episodes in the series, as this was a Halloween special released in October 2007. It has many of the conventional elements of a horror film.
This episode was conceptualized with the name "The Dark Side of the Moon."
Firelord Azulon, son of Firelord Sozin, and father of Iroh and Ozai, is the one responsible for the destruction and capture of the Southern waterbenders. After he became Firelord, he attacked the Southern water tribe.
Five flavor soup maybe based on Chinese five spice soup.
The Art of the Animated Series says that the mountain is based on Queen Mountain in Iceland.