Nature played a trick on the illithids. After centuries of battling Jazed itself for dominance, the humans began to develope psionics of their own. Their slaves became rebellious, and soon the illithids were forced forever from a world far stronger in psionics than they. After the Mind Flayers left, leaving an indelible mark in the racial memories of the humans, civilizations rose and fell.
The humans of Jazed soon met the native sentience. A form of crystal, resembling quarts, grew in some of the higher mountains. The crystals were slow-thinking, but they are alive -- and they communicated with the humans via telepathy. The crystals, unable to manipulate their environment, developed a symbiosis with the humans. Men kept the crystals safe, and the crystals served as repositories of knowledge and wisdom for men.
Borrowing from the Crystalids' own religeons, new gods arose on Gaeleth, catering to humans and Crystalids alike. The new gods, working from deeply buried memories of the crystalline intelligences, rediscovered magic. Afraid of its power, the gods drew the source of the magic into themselves. No magic would ever threaten Jazed. No mages would have power; no sorcerors could threaten; no wizards should visit. Artifacts and magical items that occasionally turned up on Jazed were soon drained of power.
The Sister Worlds War pitted the psionicists and their gods against the magic of Gaeleth and Brijanis. At first, the Jazedians were decimated, unaccustomed to fighting magic. Practice, and the introduction of a new class of psionicist, changed the odds in favor of the Jazedians. Gaeleth soon left the war, and Brijanis, after considerable losses and near defeat, destroyed most of its Gates.
With the Gates destroyed or rendered inactive, Jazed was left to itself for ten millennia. In that time, nations rose and fell, empires spanned continents and then crumbled, and heroes were born -- and died.
But the old fears remain. The Crystalids still remember the illithids. They still remember the mages.