The Caverns lie hundreds of feet underground. Inside, there is a complex system of caverns, tunnels, and passageways. For the most part, they exist under the continents. However, a few branches trail to the ocean, where they wind under the deep ocean floor. One of these branches is located in the Deep, and is simply called "The Trench". This is a section of the caverns isolated entirely from the rest of the system, believed to have formed under land and was isolated before continental drift moved it under the ocean.
There are a few open caves and tunnels that lead down to the Caverns, but the inhabitants of the system do not venture out, and any creatures from the surface that venture in are usually promptly eaten.
The Caverns are formed mainly from a limestone conglomeration, which is why the system is so extensive.
The Caverns host a range of lifeforms found nowhere else. They have adapted for an entirely subterranean lifestyle.
The basis of the ecosystem is formed by the Charips, lithotrophic bacteria that emit a faint glowing light.