Liquid Mercury is a component. It can be used by Cespenar to upgrade Angurvadal in Baldur's Gate II: Throne of Bhaal and Baldur's Gate II: Enhanced Edition.
It can be found in Sendai's Enclave in the section occupied by the mind flayers.
|“||Most smiths would be fascinated by the liquid metal in this vial. At the very least, a skilled craftsman could use the shimmering quicksilver to augment an existing weapon.||”|