Ungoliant

Ungoliant (Q. "Great Spider-monster") is a Great Enemy, the most powerful Demon ever to enter Arda. She was a Spirit of the Void (Nothingness), the incarnation of Darkness, and the embodiment of utter Destruction. One of Morgoth's earliest allies, Ungoliant rebelled against his service, for she became obsessed with light, wanting only to devouritand turn it into her own special Darkness, the Unlight, that destroyed all Light and Good things. When Morgoth later desired the Silmarilli (Great Jewels), it was no hard task for him to persuade Ungoliant to join in a raid on Valinor, for when she heard of the Jewels, she desired them for herself. She cloaked both herself and her master in her Unlight and wove webs of Darkness for them to climb into Valinor, and so they came upon the Blessed Realm in a time of festival. They then poisoned the Two Trees and fled with the Jewels.

When they reached their dark refuge, they quarreled over the spoils, and Ungoliant grew in rage to such a size and might that Morgoth himself was terrified and cried out to his Balrogs to save him. The Spirits of Fire chased Ungoliant with their flaming whips, and she fled into a dark valley. There she found other creatures of her own sort, but less great, and she and they were of the shape that the Free Peoples call spiders. There she lived and mated and reproduced. Shelob was one of her brood, and there were many others, some lesser and some nearly as great. No one knows what became of Ungoliant, but some of the Wise claim that her hunger at last became too great for her, and having already devoured her woeful mates, she proceeded to consume herself.