Ungoliant

Ungoliant is a spirit that came into Arda and took the shape of a monstrous spider, called Gloomweaver in the histories of The Silmarillion. Nothing is recorded of where she came from. Her being is darkness itself, and the form she wears reflects it; she is the eldest of the great spiders. She was once in league with Melkor and then cast off his mastery, wanting nothing but to take and devour and fill an emptiness that cannot be filled. Fleeing south, into country the Valar left unwatched and the hunters of Oromë did not ride, she came at last to the borders of the Blessed Realm and made her lair in a ravine of Avathar, under the shadow of Hyarmentir. There she spun black webs across a cleft of the mountains and drank the light of that region, twisting it into nets of strangling gloom, until no light could reach her at all and she went hungry.