Foebane

Foebane is an exceptionally powerful bastard sword that was created by Demron for Captain Fflar of Myth Drannor. It got lost under the rubble when that city fell. Its full power is only realised when it is combined with the also magical Fflar's Scabbard. Without it, it has a +3 enhancement bonus and does extra damage against all undead, shapeshifters and outsiders. Combining the two isn't simply done, though, and requires special means. With the scabbard, the sword's enhancement bonus rises to +5 and it grants +1 to all saving throws and casts Larloch's Minor Drain on its target every time it hits.

In Baldur's Gate II: Throne of Bhaal, Foebane can be found on a living statue on the first (uppermost) level of Watcher's Keep, and Cespenar can combine it with its scabbard once that is found.