Quor-Toa are fish-like humanoids that dwell in the Barren Sea of Eberron, and in the Lagoons of Piety. Quor-Toa have a distinctive appearance that resembles various species of fish. Frills, barbels and fins are common features, and individuals can look very different from each other (though communities tend to have common traits).
Their original home in the Barren Sea once held powerful manifest zones to Dal Quor, and the Quor-Toa evolved within those manifest zones, giving them a much stronger connection to the realm of Dreams than most mortals. The Quor-Toa's connection was so great that they existed in Dal-Quor and Eberron simultaneously, able to shape the essence of Dreams into reality, sculpting tools and structures from dreamstuff.
They once had a great, prosperous civilisation in the Barren Sea, working wonders that would be impossible anywhere else. They could only do this in their manifest zones, so they never sought to expand or conquer, they were content in their idyllic utopia under the seas. They defended their territory from incursion, however, and there are records from the Age of Giants of Cul'sir explorers glimpsing wonders below the "Golden Sea" and talking of the god-like beings that lived there.
Ultimately, the giants destroyed the Quor-Toa civilisation without even realising it. When the giant's war with the Quori resulted in the creation and firing of the Moonbreaker, severing Dal Quor from Eberron, the manifest zones that the Quor-Toa relied on were destroyed. The dream cities melted away, and the Quor-Toa suffered devastating psychic trauma, immediately collapsing their society into chaos and nightmare. Later generations of Quor-Toa did adjust, but they were never the same as they once were. Their knowledge, their culture, all of it was lost when the dream was broken.
Regardless, they still maintain a stronger connection to Dal Quor than any other mortals, they still exist in both realities simultaneously, and they remain psionically gifted. Dal Quor is not what it was before their shattering, however, it has become a realm of nightmares, and this has an impact on the Quor-Toa. Their powers are twisted, and many of them are existing simultaneously in Eberron and a personal hell in Dal Quor. Most interesting, they are actually still capable of pulling things out of Dal Quor and manifesting them in Eberron. Once, their cities were ruled by gods of their own making, quori collectively dreamed into shape by their people. Now, these quori are drawn from their nightmares; their gods are no longer benevolent.
The Quori avoid the Quor-Toa wherever possible, because the Quor-Toa have the power to change them.