The Burrow, also known as the Dark Roads and the World Below, is a massive, world-spanning series of catacombs beneath the surface of Erenoth. It is believed that an ancient race of titans, born of the gods and the primordials, carved these structures, for they are unfathomably large and intricate.
The Burrow is inhabited now by all manner of vile creatures, including civilizations such as the drow and duergar. During the reign of King Adelburn, many monstrous creatures were driven into the burrow, so it is a dangerous and unpredictable place. It is also utilized by the Umbercloaks as an underground highway.