This
NetHack wand produces a blast of
cold along a straight line in the direction you
zap it. This does heavy
damage to most
monsters in the path, particularly the fiery ones. The bolt of
cold will
bounce, which is illogical but can be useful. Gain
cold resistance before waving this sucker around much. Also, if a bolt of
cold hits you, your
potions may
freeze and
explode.
The wand of cold is also one of the other ways to cross the castle moat and the water in Medusa's lair if you don't have boots of water walking or some means of levitation. The bolt of cold will freeze one square of water in the direction you zap.