The Black Arrow was Bard the Bowman's last remaining arrow when Smaug attacked Laketown and, directed by a thrush who had overheard a conversation between Bilbo Baggins and Smaug, he shot it with remarkable speed into a weak spot in the left part of the chest of the dragon's natural armour of scales, killing him, and thus freeing Lonely Mountain (Erebor), Dale, and Laketown.
The Black Arrow was forged by Thrór the Dwarf, who was King under the Mountain (Lonely Mountain or Erebor), 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).
Portrayal in adaptationsEdit
The Hobbit film trilogyEdit
In The Hobbit film series, 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 windlance ballistae at attacking dragons. The arrows themselves are roughly 2 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 armoured hide of dragons.
As seen in The Hobbit: An Unexpected Journey extended edition, and again in The Hobbit: The Desolation of Smaug, during Smaug's original assault on Erebor, all but one of the Black Arrows were spent, as Girion, Lord of Dale attempted to shoot down Smaug 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 descendents.
After Thorin and Company accidentally release Smaug upon Laketown, Bard the Bowman, a direct descendent of Girion, retrieves the arrow from his home and attempts to reach Laketown’s windlance ballista, intent on slaying Smaug. However he was arrested by the corrupt Master of Laketown 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.
During The Hobbit: The Battle of the Five Armies, Bain retrieves the arrow in the midst of Smaug’s assault upon Laketown, 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.