Gnaag becomes leader of the Darklords (the fourth and last) after the death of Haakon, by means of manipulation and intrigue. He then began a clever strategy to take over Magnamund, which almost succeeds. He is the "boss monster" at the end of Lone Wolf 12: The Masters of Darkness, the last in the original series of Lone Wolf gamebooks. If the book goes according to plan, Gnaag is slain and the Darklords are destroyed.
Gnaag is also the nominal ruler of Mozgoar, although apparently resident at Helgedad.