Horn

Helm of the Rock Horns are the horns required to finish the Helm of the Rock. Like the helm, they can be found in Watcher's Keep on the second floor. The precise locations are not known. These items appear in Baldur's Gate II: Throne of Bhaal and they will probably appear in Baldur's Gate II: Enhanced Edition.

In-game description
"Despite a strong dweomer of magic, this ornate animal horn has no apparent use."