The location of the final level of Thief: The Dark Project and Thief Gold, the Maw of Chaos appears to either be the realm of The Trickster, or else possibly a gateway into said realm. The elements and chaos hold sway here, defying the laws of physics as traditionally held. A gate deep within, leading to an unknown location, continuously summons forth Chaos Beasts to join Constantine's army. All manner of minions of The Trickster lurk here, including Chaos Beasts, Spiders, and Fire Elementals. Other dangers include waterfalls that flow upwards, freezing crystals, and rivers of magma.
In general, as the Trickster is the god of chaos, the Maw is the realm of chaos. It is a magical realm, separated from the world of The City and can only be reached by portals. The Maw can however take different forms. The Trickster's works are made of the unformed stuff of the world, opposing the Builder who is the entity of order. In this direction in Thief: The Dark Project, the Maw represents a series of caves, though which the Chaos Beast army is risen. On the other side, in Thief II: The Metal Age, the Maw is controlled by Viktoria and has a different look. It feels closer to nature, with much more plants and grass than the first variation. The creatures inhabiting the Viktoria-dominated Maw are also different, but in both versions there are common elements like the giant trees, animal-like creatures and giant crystal formations.
The Maw is not seen in Thief: Deadly Shadows for unknown reasons. The Pagans instead inhabit sewers and abandoned buildings, with fewer Chaos Beasts.