J.R.R. Tolkien places the dragon Smaug inside the Lonely Mountain in The Hobbit.
Smaug seized the Dwarves’ kingdom of Erebor and its immense treasure before the events of the novel. The displaced Dwarf king Thorin Oakenshield and his companions travel with Bilbo Baggins and Gandalf to reclaim the mountain.
Bilbo enters Smaug’s chamber and uses conversation, riddles and careful observation rather than physical strength. During their exchange, Bilbo notices a vulnerable area in the dragon’s armour-like hide. He later communicates this information to Bard the Bowman, who uses the Black Arrow to kill Smaug.
Smaug is sometimes confused with Tolkien’s other dragons, especially Glaurung, who belongs to the earlier legend of Túrin in The Silmarillion. Smaug is the principal dragon of The Hobbit and is closely associated with Erebor, Dale and the treasure beneath the mountain.