Vials of Mysterious Liquid are bottles of a corrosive substance used to contaminate iron ore across the Sword Coast in Baldur's Gate. It is found on the bodies of kobolds in the Nashkel Mines. This item has no use. It is part of The Tainted Ore quest, which was cut from the game and can only be restored by installing the mod Unfinished Business by Pocket Plane.
Drinking it as a potion will cause the imbiber to become poisoned as well as permanently lose one point of Constitution.
|“||This potion contains a strange green substance similar to the residue you have seen in some of the mining carts. The liquid inside appears to discolor any iron that it comes into contact with and, and is likely related to the mysterious "plague" that renders smelted weapons and tools brittle. The Kobolds you killed must have tainted all the ore leaving the mine, though it is unlikely they would have concocted this plan themselves.||”|