Ungoliant

"[...] for here dwelt the primeval spirit Moru whom even the Valar know not whence or when she came, and the folk of Earth have given her many names." ― The Book of Lost Tales Part One, The Theft of Melko and the Darkening of Valinor

Ungoliant was the embodiment of the Void's nothingness, a spider-shaped horrifying creature purposed by an all-consuming perpetual hunger whose foul brood would continue to infest Middle-earth. Once in league with Morgoth, she disowned him and fled to Avathar where she was her own mistress.

Upon his escape from Valinor, Morgoth sought Ungoliant out and tempted her with promises of feast in return for her aid. Together, the two mortally-wounded the Two Trees, plunging Middle-earth into utter darkness. However, on their way to Angband Morgoth reneged on his promise and withheld the Silmarils he had stolen from Ungoliant. Cheated, the great spider demanded that her old master yield the jewels or else. The Foe's cries were heard by his Balrogs who, as tempests of fire, descended upon the Gloomweaver and forced her to fly with their terrible whips.

She eventually found a suitable den in Nan Dungortheb and there she spawned a vile brood of spiders that would forever infest Middle-earth and remind Elves and Men alike of the terror that was Ungoliant. What became of her is uncertain: some legends tell that failing to sate her appetite she devoured herself at last; others claim Eärendel the Mariner stumbled upon the weaving Ungoliant in his voyages and presumably slew her, ridding Arda of a dreaded enemy.

Appearances

 * The History of Middle-earth series
 * The Book of Lost Tales Part One
 * The Book of Lost Tales Part Two
 * The Shaping of Middle-earth
 * Morgoth's Ring
 * War of the Jewels
 * The Great Tales
 * Beren and Lúthien
 * The Fall of Gondolin