Liquid Mercury

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 Lair in the section occupied by the mind flayers.

In-game description
"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."