Arrow of darkness
From Ardrana
Arrows of darkness are among the most permanent and most used of enspelled arrows. If a continual darkness spell is cast upon the shaft of an arrow, it can then be used to blind an enemy. These arrows are common among Elf scouts, who carry them sheathed until there is a use for them.
Note: The arrow of darkness originally appeared in this form in The Complete Book of Elves for the AD&D game from TSR. Their use here is for the purposes of providing context for the campaign only.