Dungeons of Doom
The Dungeons of Doom is the name given to the first half of the Mazes of Menace. They are 25 to 29 levels deep. It is here that most players meet their deaths, typically due to YASD. It also contains all stores, and the vast majority of optional branches, including Sokoban, the Gnomish Mines, the Oracle, and Medusa. Consult the diagram in the article on the Mazes of Menace for a schematic showing the locations of branches and special levels.
The player starts on the first floor of the Dungeons and has to work his/her way down. Upon retrieving the Amulet of Yendor, they must then retreat through Gehennom, return to the first floor after performing the necessary ritual, and climb the stairs to the Plane of Earth.