Starfall Ore is an component needed to upgrade the Storm Star. The mace has to brought to Cespenar who can then upgrade the item. This item appears in Baldur's Gate II: Throne of Bhaal and Baldur's Gate II: Enhanced Edition.
Location
The ore can be found in Kiser Jhaeri's house in Saradush.
In-game description
| “ | This strange material comes from the core of a meteorite which fell from the heavens. The malleable ore is surprisingly strong, and radiates an inner heat. Any item forged from the alien matter would undoubtedly possess mysterious and unearthly properties. | ” |