The Black Arrow was an heirloom of the house of Girion, Lord of Dale, passed down to Bard, his descendant.
History[]
The Black Arrow was Bard the Bowman's last remaining arrow when Smaug attacked Lake-town and, directed by a Thrush who had overheard a conversation between Bilbo Baggins and Smaug, he shot it with remarkable speed into the dragon's only weak spot; a small chink in the scales upon its left chest. Smaug was felled by the shot, and the Lonely Mountain, Dale, and Lake-town were freed. The Black Arrow was forged by Thrór, who was the King under the Mountain before its fall, according to The Hobbit. It is not known if it had any magical properties, but Bard said that he had successfully retrieved it every time he used it (like Beleg's arrow Dailir). The Black Arrow is not a single regular-sized arrow, but rather one in a series of large metal quarrels, designed to be fired by a "Wind lance" ballista for attacking dragons. The arrows themselves are roughly two metres in length with heavy twisted steel heads, combining elements of both spears and harpoons. The Black Arrows are the only known weapons with enough power to pierce the armored hide of dragons.
All but one of the Black Arrows are spent on Smaug as Girion, Lord of Dale attempted to shoot him down in defence of the city. One of his shots managed to break off an armoured scale protecting the left side of the dragon’s chest. However, Girion was himself killed by Smaug before taking a final shot. It is later revealed that the last Black Arrow was kept as an heirloom by Girion's descendants.
After Thorin and Company accidentally release Smaug upon Lake-town, Bard the Bowman, a direct descendent of Girion, retrieves the arrow from his home and attempts to reach Lake-town’s windlance ballista, intent on slaying Smaug. However he was arrested by the corrupt Master of Lake-town before reaching the weapon, prompting his son Bain to instead hide the arrow in a boat, narrowly avoiding it being seized by the Master’s guards.
Bain retrieves the arrow in the midst of Smaug’s assault upon Lake-town, bringing it to Bard whilst he is attempting to shoot down the dragon with regular arrows fired from a longbow. During this exchange, Smaug attacks the belltower they are standing on, shattering the limbs of Bard’s bow. Improvising, Bard attaches his bowstring to the ruined tower’s posts and, using his son as a stand, fires the arrow into the weak spot on the dragon’s chest, puncturing his exposed skin and piercing his heart. Enraged, Smaug soars into the sky before succumbing to the arrow’s wound, his corpse falling onto the town’s burning ruins, crushing the Master and sinking his boat.