The underworld is a secret level similar to the Gnomish mines or Minetown, It can be found in one of the secret bonus level portals in the Ruins in a small fortress like area surrounded by lava and locked with gates. To open the gates you will need to levitate over a small open chasm to flip one of two levers
Once on the floor, the only way you will be able to traverse it is with a ring of levitation, or an other item that grants the ability to fly, as there is no ground to walk on apart from the spawn room, and various islands containing treasures.
- When you enter a floor with a portal to the Underworld, you will hear "the sounds of screaming in agony"
- There is a hidden portal to the Underworld behind the wall with the skull on level 5, the level between the mines and the swamp. You can hear the portal sounds through the wall, as well as the skull on the wall for clues. You have to dig with a pick or spell/staff of digging to access it here.
- A cloak or necklace of magic reflection is recommended here, as well as a staff or spell of magic missile. To combat the many demons, imps, and succubus that roam in the underworld.
- If you use the ladder found in the underworld, it will bring you to a new layout of the underworld, the only exit is through the portal by the spawn point.
- Entering the underworld, then descending down one floor via ladder, will result in the portal on the next floor leading you to Hell
- Skeletons and ghouls will also spawn here.