Further, the mountain is a symbol of adventure in The Hobbit, and of Bilbo's maturation as an individual, while to the Dwarves, it stands for the gain of beauty in return for loss of life.

After dragons plunder their hoards, the Longbeards, led now by Thrór, a descendant of Thorin, return to Erebor to take up the title King under the Mountain.

[T 3][2] In the Third Age, while the young Thorin II Oakenshield is out hunting, the dragon Smaug flies south from the Grey Mountains, kills all the dwarves he could find, and destroys the town of Dale.

They plan to use the secret door, whose key and map Gandalf had obtained from Thráin, whom he had found at the point of death in the pits of Dol Guldur.

[T 6] However, the Men of Esgaroth, supported by Thranduil and the Elves of Mirkwood, march in force to the mountain to demand a part of the dragon's hoard as recompense for the destruction.

Thorin, mad with greed, refuses all claims and sends word to his second cousin Dáin II Ironfoot, chief of the Dwarves of the Iron Hills, who bring reinforcements.

[T 3] Gimli, a dwarf of Erebor and the son of Glóin, one of Thorin's twelve companions, is chosen to represent his people in the Fellowship of the Ring; he helps Aragorn regain the throne of Gondor.

[T 9] Sauron's northern army, including many Easterlings, then attacks; Dale is overrun, and many Dwarves and Men take refuge in Erebor, which is promptly surrounded.

[T 3][T 11] The Jungian psychoanalyst Dorothy Matthews, viewing The Hobbit as a psychological quest, writes that the Lonely Mountain is an apt symbol of Bilbo's maturation as an individual, as the place where he takes on a leadership role and acts and makes decisions independently.

[4] The scholar of children's literature William H. Green calls the Lonely Mountain the fourth and final stage of Bilbo's education.

[6] Two scholars of literature, Paul Kocher and Randel Helms analyse Bilbo's journey to the lonely mountain, describing it as the goal of his quest and the point at which it is achieved.

"[T 12][9] Amelia Harper, in the J. R. R. Tolkien Encyclopedia, writes that the mountain's history, as usual for the Dwarves, was a tale of "beauty gained and lives lost".

[12] The Lonely Mountain appears in Peter Jackson's film adaptations of The Hobbit: An Unexpected Journey, The Desolation of Smaug, and The Battle of the Five Armies.