Smaug
Smaug the Magnificent; the Golden; the great dragon of Erebor
Name and Nature
Smaug was the greatest of the dragons of his day, a fire-drake of the ancient kind — “the Chiefest and Greatest of Calamities” — whose belly was cased in jewel-hard steel save for one patch where a scale was missing. He took the Lonely Mountain from the Dwarves, burnt the town of Dale, and for two hundred years glowed above his hoard.
The Quest
Bilbo came to him beneath the Mountain wearing the Ring, and in the riddling talk learned the bare patch of his armour; when the dragon flew against Lake-town, Bard the Bowman set the last of his black arrows to his bow and slew him — the fell of Smaug crashed down and crushed the old tower of the town, and his reign of fire was over.
Legacy
His death emptied the Mountain for the dwarves, and his gold and its curse drew men and elves and the goblin hosts to the Battle of Five Armies.