Most that witnessed this event still shiver in fear, the Cataclysm of the Underdark.

A series of omens and minor attacks... thralls digging, seemingly immune to attack... mages of the then great Sorcere in Udos Dro'xun, nervously predicting doom. But none could have prepared for the severity of what was soon to follow.

In one brutal attack, swarms of mind flayers attacked both Udos Dro'xun and Urblexis Grond, all but destroying both. Many were taken as slaves, thralls, food. The rest were forced to flee. In any other circumstances, it would have been impossible, but survivors were few, the situation was desparate, and so the drow of Udos grudgingly cooperated with their neighbours from Urblexis, a mish-mash of outcasts from a variety of cave-dwelling races. And they found mutual survival.

One of the Sorcere mages managed to construct a device to hold the mind flayers at bay, with the fortunate side-effect that the psionic waves prevent the residents from attacking one another. Pit Town was the result, a dingy but habitable environment that has long existed beneath the Pit of 1000 Sorrows, with some of the buildings from Udos and Grond magically transported there.

Excavations revealed a system of tunnels, ending in a waste hole: the sewers used by the very illithid who had captured so many. A covert operation now exists with the intent to free as many of the mind slaves as possible and bring them to Pit Town.

Most of the surviving former residents of Udos and Urblexis settled in Pit Town due to its relative safety, taking advantage of the protection afforded by the big thingy in the middle to trade in the relative assurance of not being literally stabbed in the back, only having to worry about said stabbing in the figurative sense.

Some of the stronger residents ventured out after the mind flayers had left in the hopes of clinging onto their old homes... some areas were not completely destroyed, and so these proud underfolk continue their lives, unsettled by the recent events but making do and forming strongholds where the destruction is least severe.