In J.R.R. Tolkien’s legendarium, Ungoliant is the giant spider Shelob’s ancestor.
Ungoliant is a primordial being associated with darkness and the devouring of light. In The Silmarillion, she allies with Melkor, later called Morgoth, during the destruction of the Two Trees of Valinor. She helps him drain the Trees’ light and then escapes with him toward Middle-earth.
Ungoliant eventually turns against Morgoth because she wants the Silmarils and other treasures for herself. Morgoth summons monstrous Balrogs to drive her away. Tolkien leaves parts of Ungoliant’s ultimate origin deliberately mysterious, describing her as coming from outside the known order of the world rather than presenting her as an ordinary animal.
Shelob, encountered by Frodo and Sam near Cirith Ungol, is described as one of Ungoliant’s descendants. Shelob is therefore not simply a giant natural spider. She belongs to a supernatural lineage of devouring creatures. Arachne is the name of a spider-like monster in Greek mythology, while Glaurung is Tolkien’s dragon and Morgoth is Ungoliant’s former ally.