Smaug is the dragon who guards the hoard in J.R.R. Tolkien’s The Hobbit.
Smaug takes possession of the Lonely Mountain, also called Erebor, after driving out the dwarf king Thráin II and the people of Dale. He settles over the vast treasure beneath the mountain and remains there until Bilbo Baggins enters the lair during the dwarves’ attempt to reclaim their homeland.
Bilbo does not defeat Smaug in direct combat. Instead, he notices a vulnerable patch in the dragon’s armored underside and later tells the information to Bard of Lake-town. A thrush carries the crucial message, enabling Bard to use the Black Arrow.
Smaug’s death does not end the conflict over the treasure. It triggers a struggle among the dwarves, elves, and Men, leading to the Battle of the Five Armies.