There is light in the dungeon. Each square is either lit or unlit. Within the range of your vision, you can see any monster or object on a lit square. This works even if the monster or object is on the other side of a room, and even if you must look past some dark squares. Corridors are usually dark. Rooms can be lit or unlit; the frequency of dark rooms tends to increase at deeper dungeon levels. Occasionally, entire dungeon levels will be dark, particularly in branches such as Gehennom or the Gnomish Mines.
- Walls and closed doors limit your vision. You cannot see into another room, unless you look through a suitable passageway.
- Light is useless when you are blind.
- There are ways to cause darkness, such as by using a cursed scroll of light.
- Some locations, such as under water, cannot be lit. You can light the inside of a vortex, if engulfed, but there is little reason to do so.
There are ways to make more light:
- permanently, with a scroll of light, wand of light, or the spell from a spellbook of light.
- temporarily, by switching on a light source such as an oil lamp or magic lamp. (Sometimes you might want to switch it off again, because lamps reveal your location to monsters or because light sources other than magic lamps burn out eventually.)