The Moonstones quest is began by speaking with Captain Tillin in the South Qeynos arena (Warrior Guild). He informs you of the Gnoll menace that dwells in the nearby Qeynos Hills and requests for you to bring him Gnoll Fangs as proof that you have slain some of the beasts. Captain Tillin also offers you a Moonstone for every fang you bring him. These Moonstones are wanted by Mcneal Jacub in a tavern named Fish's Ale in South Qeynos.