A yellow light attacks the hero by exploding when adjacent (destroying itself in the process), causing blindness but no other damage. The blindness will last for 10d20 turns.
The explosion of a yellow light will wake nearby sleeping monsters.
The best course of action is to put on a blindfold or towel and wait for it to explode, or to have a blindness cure ready. If it is invisible and you do not see invisible, there is a chance based on your level that it will not affect you. This will generate the message "Something explodes, but you get the feeling it wasn't too bright".
Strange creatures formed from energy rather than matter,
lights are given to self-destructive behavior when battling