True to its name, this NetHack potion
ed. The blindness will last from 125 to 575 (or maybe more) turns, which can obviously cause problems. Good insurance
against accidentally quaffing one of these is telepathy
or a unicorn horn
This potion can be thrown at monsters to blind them instead. If you inhale the vapors of a smashed potion of blindness, you will be blinded for 1-5 turns.
Additionally, dipping a unicorn horn into this potion will change it into uncursed water.