WARNING! This article contains information from the web novel. Do not proceed unless you want to be spoiled.
Hell (地獄,Jigoku?) is a world that exists in one of the nine alternate realities. It can be accessed by the "Mirror Gate" Sacred Vessel located in the Vatican. The 'Humans' of this world have either migrated to Earth and interbred with its populace, or they stayed behind and became the entities known as 'Demons' in Earth mythology and religions. The demons are without flesh and consist of only souls due to the environment having been decimated long ago. There are 9 stratums where these 'Demons' live and the lower levels are ruled by Seven Kings, each with a level of power and presence comparable to Ehit, as noted by Yue. Like the other eight worlds, it possess a tree that acts as a branch of the World Tree of True World Astral, which Hajime has named "Demon Tree".