Though, with the help of Gandalf the Grey Wizard and the Hobbit Bilbo Baggins, Zorin Oakenshield, the Dwarf prince of the Lonely Mountain, later led his warriors back to the Lonely Mountain, drove away Smaug, and reclaimed the sacred homeland of the Dwarves. In gratitude, Zorin Oakenshield even gave Bilbo an extraordinarily precious mithril shirt. But the Dwarves' obsession with mining had not been frightened away by Smaug in the slightest. They still dug frantically all across Middle-earth, stockpiling every kind of underground mineral deposit. Even if they could never use it all, they happily kept digging!
The most fanatical of them were the Dwarves of Moria, led by Balin, Gimli's cousin!
The history book Gandalf had been reading recorded that Balin had led this group of Dwarves to mine Middle-earth's largest mithril vein day and night. They had been utterly bewitched by chunks of mithril ore gleaming with mysterious light. Ignoring the priests' warnings, they desperately dug deeper and deeper underground in pursuit of more mithril ore. To transport it, the Dwarves of Moria under Balin's command had actually built an "Endless Stair" from the depths below, stretching so far its end could not be seen, all the way up to the surface of Moria—the enormous bottomless pit they had seen earlier!
But at the underground terminus on the other side of that "Endless Stair," the Dwarves' old obsession with digging finally caused them to stumble upon another dreadful nightmare: the ancient Balrog sealed within the abyss beneath Khazad-dûm!
Unlike Smaug, whose love of treasure represented greed, the ancient Balrog represented destruction and ruin. It was practically the avatar of death itself. Though Smaug had inflicted grievous casualties upon the Dwarves of the Lonely Mountain, he had at least not wiped out their race; he had merely driven them