The Labyrinth was a network of lava tubes tunnels made of cold black basalt. There were some paths and bridges. Depending on who was describing it, the tunnels either spanned 100 miles north to south and more than 50 miles east to west, or 200 miles north to south and almost 100 mile east to west. Runes were carved into the tunnels to guide travelers, but few could read them. There were a number of rifts that cut through the Labyrinth, so many tunnels emptied into massive chasms or dead-ended. Some staircases have been carved into stone to overcome these chasms.
Although there were a few well-documented paths used by merchants and travelers from Menzoberranzan and Gracklstugh, travelers who wandered off the known paths were bound to get hopelessly lost and starve to death or be killed by the minotaurs that inhabited the tunnels. As well as minotaurs, a fallen angel, known as Baatral, inhabited the labyrinth.
A number of portals were located in the Labyrinth. One led to the wilderness near Ched Nasad, another to Oryndoll. One led into Ammarindar. Another portal in the former holdings of House Jaelre led to the forests of Cormanthor.
It was commonly believed that minotaurs had created the tunnels, but in fact the tunnels were originally built by a cult of demon-worshiping dwarves of Ammarindar ca. −2200 DR. The dwarves worshiped Baphomet and allied themselves with minotaurs and bull-headed demons. They also had at least one portal constructed in the Labyrinth, which led to their home in Ammarindar.
A few centuries after the dwarves disappeared, the region was settled by baphitaurs, which were created by the Netherese wizards of Andalbruin through the experimental merging of humans, minotaurs, and demons. Eventually, the minotaur civilization fell to war with their neighbors and a brutal civil war.
The quieter parts of the Labyrinth often served as the homes of exiles and loners. Of particular note was House Jaelre, who resided here after their exile from Menzoberranzan for a time before they moved on to Minauthkeep (the Elven Court) in Cormanthor.
- Pit of Howling Grief
- The Pit of Howling Grief was a rift in the ground filled with endless sounds of moaning and wailing. Next to the chasm was a slab of black rock that served as an altar to the demon lord Baphomet.
- Bruce R. Cordell, Gwendolyn F.M. Kestrel, Jeff Quick (October 2003). Underdark. (Wizards of the Coast), p. 158. ISBN 0-7869-3053-5.
- James Wyatt (2002-09-04). “The Shadow Path: A Portal Network”. Perilous Gateways. Wizards of the Coast. Archived from the original on 2004-02-23. Retrieved on 2014-03-27.
- Richard Baker (May 2003). Condemnation. (Wizards of the Coast), p. 17. ISBN 0786932023.
- Richard Baker (May 2003). Condemnation. (Wizards of the Coast), pp. 152–154. ISBN 0786932023.
- Richard Baker (May 2003). Condemnation. (Wizards of the Coast), p. 173. ISBN 0786932023.
- Greg Bilsland. Thunderspire Labyrinth Forgotten Realms Conversion (PDF). Dungeon magazine 156. p. 29. Retrieved on 2017-01-31.
- Richard Baker (May 2003). Condemnation. (Wizards of the Coast). ISBN 0786932023.