Tansheron's Bow

Tansheron's Bow, also known as Tansheron's Shortbow, is an enchanted weapon +3. Unlike normal ranged weapons, this bow creates its own arrows which deal 1d6 points of damage. The bow can create unlimited arrows and use physical arrows from the ammunition slots as well. It's not recommended to fire non-enchanted arrows from this bow, because the bow's arrows deal the same amount of damage and you could waste ammunition slots which could be used to store other ammunition.

The bow has a range of 75 feet, which is standard for short bows. This item appears in Baldur's Gate II: Shadows of Amn and Baldur's Gate II: Enhanced Edition. This bow can be bought in Trademeet from an unnamed merchant after solving the genie problems.

In-game description
"Tansheron's Short Bow +3 The thin, frayed string of this bow appears unusable, but when it is drawn a solid but invisible arrow becomes tangible. The lich Tansheron gave this bow to his Watcher, the guardian of his keep who stood atop a tower with neither entrance nor exit. When anyone approached, down would fall a never-ending rain of phantom arrows until they were dead or fled. How this bow was wrested from the Watcher's hand is not known, but would probably make a great tavern story.

Note: avoid equipping normal arrows on your character, else the bow will fire these instead of the phantom arrows."