Reguare is an isolated expanse of Nar-Voth that lies beneath the ancient holdings of Ghol-Gan empire. The so-called Sleepless Realm was cut off from the rest of the Darklands during Earthfall, and many of the entrances that connect Golarion's surface to Reguare were buried at the same time.
Among the few passages that remain are a tunnel buried beneath tons of rock and rubble in the catacombs under the infamous fortress of Eel's Skull on Nalt's Island, and a hidden entrance beneath the Crimson Citadel of the Red Mantis assassins on Mediogalti Island.
There is only one major tunnel that runs through Reguare, called in ancient times the March of Madness. Much shorter than the Long Walk, the March of Madness features halls of cyclopean size and its caverns, hundreds of feet tall, were obviously home to colossal creatures. Strange inscriptions on the walls sometimes span from floor to ceiling.
Scholars suggest that the cyclopes of Ghol-Gan captured and tamed purple worms or other slithering behemoths to use as mounts in their wars against the serpentfolk, and the March of Madness served as a valuable passageway for Ghol-Gan cavalry on their campaigns. Some caverns within Reguare contain primordial jungles, and many hot springs and lava vents draw treacherous monsters.1