In Baldur's Gate, Arla's Dragonbane can be found in the tower of Durlag on the fourth floor among the ornate graves, protected by many traps. This is the most powerful sling available in that game and a very powerful missile weapon.
In Baldur's Gate II, this weapon can be found in the Ruined temple of Amaunator found in the Temple Ruins area.
|“||Sling +3: 'Arla's Dragonbane.' None know better than Halflings the value of a well-placed stone when confronting a larger foe. This particular weapon was the property of a young woman named Arla Surestep, one of the few small-folk that leave the hearth to seek adventure. Legend speaks of the diminutive Arla using this sling to place a well-sharpened pebble through the skull of a green dragon in mid-flight, though the same tale in another tavern places the stone squarely in the creature's hindquarters for more humorous than lethal effect. It would seem that Halflings prefer entertainment over accuracy when it comes to their history.||”|