Namarra

Namarra is an enchanted longsword +2, but unlike a Long Sword +2, it has +4 damage bonus instead of +2, but they have the same weight of 3 lbs, both a speed factor of 3 and -2 THACo bonus. This weapon can also be used to cast Silence, 15' Radius three times every day, which makes the weapon useful against spellcasters.

This item appears in Baldur's Gate II: Shadows of Amn and Baldur's Gate II: Enhanced Edition. This weapon can be found in Athkatla Graveyard. It's wielded by a powerful undead in a crypt who drops when its killed. The crypt is close to entrance of Bodhi's Lair.

In-game description
"Namarra, Long Sword +2 Also known as Neversleep, this ancient blade is thought to have been present at some of the most influential conflicts in Faerun's history. Sightings have been noted as far north as Thay and as south as the jungles of Chult, though documentation is oddly lacking regarding the details. It is perhaps a result of the sword's ability to silence all sound within a large radius, removing the effectiveness of attacking mages but also preventing any discussion that might have followed."