Light and shadows are at play in every location of the world. Some locations
(especially those underground with no natural light source) will be dark,
while others may be under a constant influence of light. Day and night time
can also affect how bright a location is, especially outdoors. Certain objects,
such as torches and lanterns, can add light to a location and there are many
enchantments which are known to cause items or an entire room to glow.
Brightness and darkness are represented by a numeric value, ranging between
-200 (pitch black) and +200 (blinding light). To assess the luminosity of
your current location, type ILLUMINATION.