Father of the Dragons of Middle Earth, though not the greatest. A four-legged fire-drake. Titles include The Great Worm, the Father of Dragons, Morgoth's Worm, and Glaurung the Golden.
He made his first appearance approximately two hundred years after the Dagor Aglareb while he was still half-grown, rampaging through Ard-Galen. He was turned back from this youthful adventure by Fingon of Hithlum and his archers, who were able to drive him off because his scales were not fully developed.
Glaurung's next appearance in Middle-Earth came in the Dagor Bragollach, when he, grown to his full strength and power, shattered the siege of Angband, destroyed Lothlann, and ravaged northeast Beleriand.
After this, he took part in the Nirnaeth Arnoediad, again shattering the armies of the Noldor. He was defeated by the Dwarves of Belegost, whose heavy plate armor and metal masks offered some protection against the dragon fire.
The Father of Dragons next led the sack of Nargothrond, stopping along the way to trash all the surrounding lands. Hypnotized Turin Turambar in their first confrontation, sending him into the wilderness chasing after lies and deceptions. Later erased the memory of Turin's sister Nienor, an act which later led her to marry her brother. Finally, he was stabbed to death by Turin at Cabed-en-Aras.
The full story of Glaurung, Turin, and Nienor, while a great epic tragedy, is beyond the scope of this writeup. Anyone interested can find the condensed version in chapter 21 of The Silmarillion or the full-length version in the book of Unfinished Tales by J.R.R. Tolkien.