Shelob

Warning: Wikipedia contains spoilers

Shelob is the man-eating creature in spider form, high in the mountains of Mordor. She is the last of the spawn of Ungoliant. Her lair is along the path that Sam Gamgee and Frodo Baggins take while seeking Mount Doom. Apparently she had some sort of understanding with Gollum, whom the orcs of the Tower of Cirith Ungol call "Her Sneak".

She originally occupied Cirith Ungol, and may have occupied Beleriand, possibly in the Ered Gorgoroth[?].

Her children (upon whom she often fed) included the giant spiders (but much smaller than Shelob) who captured Bilbo Baggins' dwarven allies in Mirkwood Forest.