Smaug

Smaug is presented in Tolkien's narrative as a dragon who came from the dragon-haunts in the Withered Heath beyond the Grey Mountains. He 'arose and without warning came against King Thrór and descended on the mountain in flames,' drove out the Dwarves of Erebor, destroyed the nearby town of Dale, and thereafter occupied the interior of the mountain for roughly 150 years guarding a vast hoard. The invasion of Erebor is dated in the narrative tradition as occurring 171 years before the events of The Hobbit.

Smaug is described as a winged, fiery, reptilian being with an armoured, jewel-encrusted belly; Bilbo notices 'a small bare patch on Smaug's jewel-encrusted underbelly' which is crucial to the plot. He is centuries old, of great size and destructive capability (able to destroy towns), and possesses wings and the ability to fly and breathe fire.

Smaug is a cunning, speaking dragon who guards a vast hoard and knows its contents 'to the ounce,' immediately detecting the theft of a cup. He breathes fire, flies, and can lay waste to settlements (he destroyed Dale and later attacked Lake-town). He demonstrates keen perception—sensing Bilbo's presence despite Bilbo's use of the One Ring to be invisible—and engages in prolonged conversation, showing vanity and wiliness. Ordinary townsmen's arrows and spears 'proved useless against the dragon's armoured body.' His death results from a single small bare patch on his underbelly being struck by Bard the Bowman after a thrush relays the information.