Shelob was a great Spider who escaped the Ruin of Beleriand in the First Age. She dwelt in Mirkwood for a long while until finally moving to the Pass of Cirith Ungol, into Mordor. Sauron used her as a guard to his realm, and would occasionally send parties of Orcs to provide her with food. Shelob died some time in the Third or Fourth Age, either by Sam's wounds or by lack of food.