Gorbag was the captain of a company of Orcs from Minas Morgul, the city of the Nazgûl on the western side of the Ephel Dúath.1
On the night Shelob stung Frodo, Gorbag's company came up the pass of Cirith Ungol from the Morgul side as Shagrat's Orcs came down from the tower, and the two met over Frodo's body. Sam, wearing the Ring, followed them and heard the captains talk. Gorbag was the more uneasy of the two: he grumbled about the Nazgûl who commanded his city, and spoke of the war as something that might yet go badly, and of slipping away with a few trusty lads to set up somewhere on their own.1
Lugbúrz's standing orders, as Shagrat recited them, were that a prisoner be stripped and held in the tower, and that a full description of every article of his gear be sent to Lugbúrz. But the Orcs wanted Frodo's mithril-coat, and the quarrel over it turned into a battle through the whole tower, in which nearly all of both companies were killed.1,2
Gorbag, wounded and left for dead, crawled up and clutched at the bundle of Frodo's belongings in Shagrat's hand, and tried to spear him; Shagrat killed him and made off. Their feud left the tower almost empty, which is how Sam was able to reach Frodo and free him.2
Sources
Citations name the chapter rather than the page, so they work in any edition. The colour of each note shows what kind of source it is.
- Published story The Hobbit and The Lord of the Rings as Tolkien published them.
- Published story The Two Towers, Book IV, ch. 10, “The Choices of Master Samwise”
- Published story The Return of the King, Book VI, ch. 1, “The Tower of Cirith Ungol”