The setting is being fleshed out as we go, but here's what I have so far.
The civilized world consists of numerous mountaintop settlements that formed when the low lands became uninhabitable. Secluded from one another for centuries, travel and trade between colonies has been made possible through the recent advent of airships. The land below holds many ruins, but is extremely hostile and unusable for transport.
Only a generation ago, a race of aliens known as illithids found a way to the planet through some sort of gate effect, which sparked the birth of psionics. The event is now known as The Awakening. What they seek is unknown, but they don't hesitate to kill any in their way, in the most brutal of fashions. They were tracked here by a race called the githyanki, who use an unparalleled technology to aid them in their en devours.