Ungoliant

Ungoliant was first sighted in Avathar, a dark and cold region in the south of Valinor. Where she came from no one knows, but it was said among the Eldar she came down to Eä and was corrupted by Melkor, but she had dismastered him, desiring to be her own master. She took the shape of a monstrous spider, sucking in all light, and from that light spinning forth dark webs of gloom, until no light came to her in her dark abode. Now at that time Melkor came to her abode and offered her a partnership in his designs. Ungoliant was torn between lust and fear, for the might of the Ainur in their bliss was strong indeed. Then Melkor promised her to give her with both hands to still her hunger if she did what he asked. At this Ungoliant yielded and spun a great darkness around them and both set forth into Valinor. Now this was a time of a great feast and they reached Valinor without being seen, both escaping the vigil of the Valar as well as covered by Ungoliant's dark cloak of weavings.

Quickly they came upon the mound on which Telperion and Laurelin grew and Melkor smote them with his spear and Ungoliant sucked them dry. After drinking from the two trees, Ungoliant grew to a size so fast and hideous even Melkor grew afraid. Quickly Ungoliant and Meklor fled from Valmar with all speed to the north, while Ungoliant spun forth a dark greater than dark, which even discouraged the most valiant of the Valar. Soon after that they came upon Formenost, where Finwë, father of Feanor dwelt, and where the Silmarils were locked away. Melkor then slew Finwë and took from Formenost a great treasure in gems and the Silmarils.

Later as they reached the Firth of Drengist, Ungoliant stayed Melkor, and demanded him to fullfill his promise. Melkor than gave her all the gems he had taken from Formenost save the Silmarils only, and those gems perished from the world. After devouring those gems, Ungoliant grew even bigger yet, and demanded Melkor to yield the Silmarils to him. Melkor refused this and Ungoliant set on him, spinning forth a terrible web of blackness about them. Melkor then cried out a terrible cry, which was heard by his Balrogs which had remained hidden within the dark dungeons of Angband, awaiting his return. Now quickly they came forth and rent asunder Ungoliant's dark cloud with their whips of flame and she fled south.

Now after that, nothing was ever seen or heard of Ungoliant again, but it is certain she fled to Ered Gorgoroth, mating with lesser spiders and devouring them, leaving that place a place of dread, shunned by any living being, save those of evil purpose. It is said she fled even further south, mating and devouring until at last utterly famished, she devoured herself.