Ooltul was known as The City of Tyrants, an appellation earned long ago by the fact that it was founded and governed by the eye tyrants. It had been a great city, once, with homes built into the massive stalactites hundreds of feet above the cavern floor. The centerpiece of the city was a vast tower, Zorx-ka, that stretched from floor to ceiling, honeycombed with tunnels and lairs. The floor had been reserved for the lesser races, visiting merchants and slaves. It had been a vibrant, powerful city, a hub for traders and merchants.
Unfortunately for the beholders, they encountered an even greater form of tyrant. The phaerimm, a race of twisted, powerful extraplanar magi. Sadistic and voracious, the phaerimm had attacked the races of the surface, laying waste to great swathes of land and slaying many. The danger had become so great that another extraplanar race, the sharn, had stepped in. The phaerimm had been overpowered and imprisoned in the vast area of the underdark in which Ooltul sat by the sharn, who apparently had no qualms about sacrificing the underdark races to protect the surface from their depredations. The surface dwellers were terrified that they might break free, but the underdark races were left to deal with the threat head-on. Among the kingdoms threatened had been Ooltul. After centuries of conflict, the great city had fallen to the worm-like fiends, and the beholders themselves became slaves in their own city.
That was many centuries ago. The City of Tyrants was no longer so great, the lower levels had fallen into disrepair and few risked doing business in a city ruled by phaerimm. A Triumvirate of phaerimm now ruled, with the hive mothers answering to them. The masters had become slaves, or worse, fodder for experiments by phaerimm seeking a way to break free of their bonds.
Now the entire underdark was in a state of great unrest and confusion, particularly among the drow. With the death of Eilistraee, the defection of Selvetarm and Lolth's power slowly waning, no one knew what the great drow empire, with its millions of wicked dark elves, would do. Even the phaerimm were concerned with the power struggles taking place around them.
That did not matter to Her. She knew how it would end, and how it had began. She knew all things. Not even Ilsensine could comprehend Her great wisdom. And She knew that now was the time to act in behalf of Her children.
The proud beholders had long chafed under the yoke of the phaerimm, but lacked the power to overthrow them. Revolt after revolt had been ruthlessly crushed. The phaerimm had altered their forms, twisted their bodies. They had even lain their eggs inside some of them, their parasitic grubs devouring the unfortunates from within. The beholders had prayed for deliverance, but no one had truly expected what was to come.
She seemed to glide from the walls of the cavern itself. She was majestic. Her massive form was covered in encrusted gems, stones, armor, even intact skeletons of various races, including at least one dragon. She floated over the city, Her eyes searching almost blindly, Her great maw drooled as She gibbered in a language only She understood. And when the beholders saw Her, they rejoiced, even as the phaerimm cringed in fear. The Great Mother had come to deliver Her children.
The Day of Judgment had come, and the phaerimm had been found wanting.
She circled the massive central column of Zorx-ka at its midpoint, carefully avoiding the massive stalactite lairs of Her children that covered the ceiling of the cavern. A blinding light struck a small knot of phaerimm, and their worm-like forms, now stone, were shattered as they fell. The jubilant beholders swarmed from their homes and abandoned their duties to attack their hated masters as The Great Mother continued to rain death upon the oppressors of Her people. The powerful magics of the phaerimm availed them not as they tried in desperate futility to fight off both the avatar and Her subjects. They could not flee, no matter how desperately they desired to do so, due to the sharn's magical bonds. They were trapped within their own domain. Those phaerimm the goddess did not personally destroy fell before the vengeful eyestalks of their former slaves eager to avenge wrongs both real and imagined at the hands of their masters.
When The Great Mother vanished, gliding serenely through the stone walls of the cavern, every phaerimm in Ooltul was dead. The triumphant beholders gave thanks to their goddess for their deliverance and feasted upon the remains of their masters.
Ooltul, City of Tyrants, would shine once again.
I read about Ooltul in Drizzt Do'Urden's Guide to The Underdark, and figured it would be a good way to introduce The Great Mother into a story. I don't know if phaerimm are edible or not, but they are for the purposes of this story.
Update - According to The Forgotten Realms Campaign Guide Ooltul was invaded by the Netherese and the phaerimm were massacred. It didn't say whether or not the beholders were slain as well but noted that there were living beholders in the area, (along with beholder and phaerimm ghosts). The city itself was badly damaged in the battle.
This, of course, is my story universe, so things worked out differently.
Beholders are evil, merciless slavers as well, so they're not really innocent victims.
According to TSR, The Great Mother's avatar is 18' in diameter, but beholders in my stories are much larger than in canon, so the avatar is at least double that size. Also, in my story universe, Selvetarm was freed from Lolth's control and redeemed. My stories The Legend of Uru Drowbiter, Heroes , Monsters, Old Friends and The Broken Web all tie together in that universe.