Control a group of Elves, Men, Dwarves, Orcs, or Freebooters as you attempt to make the treasure of The Lonely Mountain your own. In order to accomplish your objective and escape, your characters must avoid or overcome traps, Fell Beasts, Trolls, Giant Spiders, Wights, Giant Sankes, and last but certainly not least: SMAUG, one of the greatest Dragons in Middle-earth.

The Lonely Mountain is an adventure game played by 1 to 6 players. Each player controls a group of adventurers attempting to sneak into the Lonely Mountain (Erebor) and steal as much loot as possible. However, they must escape before Smaug the Dragon awakens, discovers their trespasses, and slays them all. The game takes place relatively soon after Smaug attacked and drove out the Dwarves in Third Age 2770. At that time, Smaug had not yet sealed all of the minor entrances, and he considered the entire inner complex of rooms and tunnels to be his "lair". Thus adventurers can enter (and hopefully leave) in a variety of ways. A such as the one this game depicts could have been the event that caused Smaug to close all the minor entrances and to gather most of Ereborīs loot into one huge pile.

The game is played on a board representing the inner complex of rooms and tunnels where Smaug and most of the "treasure" of the Lonely Mountain reside. The board is highly abstracted and simplified to make play quick and easy. Four of the available groups of adventurers represent the interests of the four major races of Middle-earth: Dwarves, Elves, Men and Orcs. The "Freebooters" are an independent group of adventurers out for glory and loot. Each group has the same mix of 10 characters: 1 Mage, 1 Animist, 1 Bard, 1 Ranger, 2 Scouts, 2 Archers, and 2 Fighters.