The Mamming Hills were a desolate area of Unkerlant that contained mines of Cinnabar, the material which dragons needed to eat in order to breath fire. Cinnabar being thus a key munition of war, the Mamming Hills were an area of prime strategic importance. Garivald was one of the very few prisoners who ever managed to successfully escape from the Mamming Hills - his success due in considerable measure to his dormant magical powers of which he was himself almost completely unaware.