Aboleths have long been the bogeyman of the sector. Their ability to remember everything their ancestors knew and learn even more by eating other sentient beings resulted in a race of planners and lurkers.
Machoth is the capitol of the Dreamsphere system. Situated at the equator of the ocean planet Ehalla, it is partially submerged, plunging several thousand feet below the waves, and towering hundreds of feet into the air. Even the above-water parts have aboleth-sized canals running through every part, with elaborate lock systems serving as elevators. Fed and powered by countless Decanters of Endless Water, the overall effect is of constant, flowing waterfalls. As the hydraulic mechanisms rise and sink, the falls shift and flow. The spray alone forms countless shifting rainbows. The unearthly effect is multiplied by many generations' use of of illusory walls, such that the shifting water flows, spray, and wall decorations form countless discrete spaces, each containing no apparent form. Characters with very high will saves or with True Seeing active are often disconcerted in this environment: where someone failing their saves sees only a small part of the overall chaos, anyone seeing through the illusory walls will see many such spaces, all at once.
Two centuries ago, this is where aboleths would meet their trade partners and house their guests. Today, very few drylanders remain. Instead, Machoth has become the center of the Reclaimers' expansion. Most of the canals have been enchanted to bless water flowing through them, turning it silvery-white. The water continues to flow and fall as before, spreading out into the ocean for miles around the city. This has only added to the city's disorienting effects.
Far below the waves, Iathu is held in a secret prison.
The aboleth homeworlds have been surrounded with “reefs” of illusory and real walls for as long as other civilizations' history records. Extending these reefs is viewed as a community service, and so is often part of an agreed-upon criminal sanction or public works project. This, combined with the aboleths' insularity and penchant for absconding with anyone whose protections lapsed had minimized their contact with the outside worlds. The Dreamsphere has also historically been surrounded by territory claimed by The Free Traders on one side and by the precursors to [Uropater] on the the other. Negotiating passage with either could be a dicey proposition, further reinforcing the Dreamsphere's isolation.
Nonetheless, a small number of trade caravans consistently wound their way to Machoth each year. There, they most often exchanged rare spell components for information or thought bottles (an aboleth specialty).
Two centuries ago, everything changed for the Dreamsphere, when an aberrant young aboleth named Iathu founded the Reclaimer movement.
Aboleths had never previously interacted with religion. Their collective memory predated every god they encountered, which undermined many claims to divinity. Their relative isolation had protected them from most missionaries, and those few who made the difficult journey had even fewer converts.
Iathu was born with strong memories of Hagothul, who claimed to have created the Aboleths to rule Wildspace. He received further messages from him every day. When he was arrested fro street-preaching, trial was by cannibalism (standard practice, followed by regeneration). His jurors were immediate converts, and the religion exploded from there.