Darkness reduces ones ability to fight (how do you even see who to fight and where to hit really??) as well as reducing all text from combat into, “You hit Someone” and “Someone hits you”. Darkness also rids you of all information about the enviroment (even the room’s title/name).

However some classes are able to use darkness (or even need darkness). After a certain level, monks are able to use darkness to their advantage fighting as if they could see. Necromancers, however, draw their power from the dark, and are able to see even in the depths of magical darkness.

see also Light, Light Sources, Classes, Races, Darkness Sources