An Astral Stronghold.
Under normal circumstances, only the strongholds of three races could be encountered in the boundless Astral Plane.
They were the githyanki, the githzerai, and the ancient mind flayers. As mentioned much earlier, in the distant past, the mind flayers had created a brilliant extraplanar civilization, using the Astral Plane as a transit hub to control and enslave vast numbers of other races. The duergar and githyanki had both been victims of the Mind Flayer Empire, even being forced to develop innate psionics during their long enslavement.
The mind flayers had used psionics, also known as psi energy, to develop an exceptionally powerful interstellar civilization.
They were an alien species from another world, and it was even said that the first mind flayers to arrive here had come aboard an enormous astral ship. The destruction of the Mind Flayer Empire had allowed the githyanki to inherit a wealth of valuable knowledge and abilities. Compared with the innate psionics the duergar had gained, the githyanki had obtained far more valuable knowledge. They had learned how to build Astral Strongholds, mastered highly advanced forging techniques, and adapted to life in the Astral Plane. As wicked as bandits, they used the Astral Plane as a springboard to plunder the resources of other worlds.
Githyanki could appear on any plane.
Their people used Astral Strongholds as their bases and might venture into any world they could reach.
The githyanki loved plundering.
But when their targets were powerful enough, they also learned to trade fairly. In the Lower Planes, evil githyanki conducted all manner of trades with yugoloths using goods from the Astral Plane.
As for the other race, the githzerai, the path of the monk prevailed among them, and they had not dealt with humans for many years.
The githzerai pursued the