Blackmist

Blackmist is a +4 halberd that allows the wielder to cast Blindness three times per day.

Baldur's Gate II: Shadows of Amn

 * Ust Natha - it will be given to Gorion's ward by the Lesser Demon Lord if he triple cross Matron Mother Ardulace and Phaere, offer him Adalon's real eggs and ask him for a powerful magic item. Adalon won't appreciate it, though.

In-game description
"This was the weapon of Dominique Harl, a sightless paladin who frequently traveled Faerûn. When attacked, Dominique would unleash the black mist that is this halberd's namesake, potentially blinding all within 10 feet. This often gave him the advantage, for he lived in darkness all his life, seeing only with the inner light of faith. Dominique eventually fell, his body found in a dark forest, slain by a creature of the night even more at home in the shadows than he."