The Great Spiders or Ungoliant-spawn were a race of giant spider-like creatures that were bred in Dol Guldur by the Necromancer. They were released on Greenwood and brought a sickness upon the forest. It started to be known as Mirkwood due to the great sickness. Shelob was a Great Spider that eventually ventured near Mordor and took residence for years near Cirith Ungol.
History[]
The first Dark Lord, Melkor, used Ungoliant to help him destroy the Two Trees of Valinor and steal the Silmarils. Ungoliant, who had an insatiable desire to devour light, demanded the Silmarils. Melkor refused and she attempted to kill him. Ungoliant was subsequently driven off by Melkor's Balrogs, and she ultimately wandered across Middle-earth, consuming anything that gave light such as gemstones; and often mated with other large spiders. Her offspring were a great bane on the world in later years. She was described as surrounded by "an aura of darkness". Her fate is unknown, but it is said that, always hungry, Ungoliant ended by devouring herself.
Giant Spiders lurked in Mirkwood and encountered Thorin and Company
The hobbit Bilbo Baggins and his thirteen Dwarf companions encountered giant spiders in Mirkwood on their Quest to the Lonely Mountain. They managed to capture and entangle in webs each of the thirteen Dwarves. Only Bilbo's magic ring and his Elven blade (Sting) allowed them to escape from being eaten.
Shelob's lair was found near Cirith Ungol
Frodo Baggins and Sam Gamgee encountered the lone, giant spider Shelob in her lair, within caves near Cirith Ungol, as they were trying to enter Mordor in their quest to destroy the One Ring. Frodo was ambushed by her twice, and paralyzed by her poison on the second encounter. Sam used Sting to attack Shelob and wound her, which caused her to flee. Her fate is unspecified.