I don't know what it is. I can't get the idea of a sand sea out of my mind. Saliors of the DryLands...
By the way, Kalazar in one of the most cosmopolitan city states in The Dry Lands (Insert name later).
The Sun in unmerciful in its heat and relentless shining.
This could be a geologically ancient and stable world, where the mountains are mostly worn down, the land is flat, and the seas are shallow.
You might have a couple of moons, and when they both full together, the tides are extra high and come rushing across the flats. The hurricanes in this place could be truly awesome, and they'd bring storm surge with them, which covers the shore with (plant-killing) sea water (if we go with the salt options).
The Drylands recieve preciously little rain every year. The sparse populations (when compared to other water rich environments) huddle around water sources.
Cities and Villages are built into Hills and Great Mesas, where the deep rock can keep things cool.
Between the cities is the vast wastes of the Dryland. There are two ways I see them.
1) As a vast uneven salt surface. Some of it will be pancake salt, in other places it will be more granual salt. Sometimes it will be a shallow supersaturated salty sea. Skiffs would have both wheels and skis/ with a boat like feel to make this work. It would make skiffing tougher and more challanging.
2) Sand, with black bits. These black sands have magnetic properties. Between the Wind and Lightning Storms, the sand dunes would shift and roll, yet not blow up as much as real sand. Skiffs would have energized ski's with their sails to skim in and over the sand.
There could be an odd alien ecology on the surface and beneith the surface of the Drylands. The undersurface would be a vaguely marine analog. Allowing us for monsters of the deep. The surface monsters would be a cross between swamp and desert creatures. Dark Sand allows us for more interesting monster life and more metals here.
I forsee magic as a ritual affair requiring a magical laboratory/ sanctum. Many magic users will hide their laboratories, so people will not know they are mages. Most spells will be of the scrying and weather effects sort. However, summoning demons might be a secret past time. (The Black Sand could be used in spell casting, allowing for sand form/ phantasmal forms.).
Alchemy is probably the prefered form of magic here. Magic using Adventurers are probably unheard of, as they need all their stuff to do magic.
I see combat as a ritual thing as well, with lots of whirling and martial arts moves. Jumping and Leaping would be important here, as it will let you get out of the way of "breaching" Drylands life. Perhaps the social rank determines how long a reach your weapon can have. Those with spears are nobles, those with knives are commoners...
--human and animal life will tend toward the nocturnal or subterranean. Both to get out of the sun, and to conserve water (cooler night air doesn't absorb moisture as fast). Human architecture will be massive (insulating the heat out) and include lots of covered walkways, porches, etc. for shade.
--life is all about water in this place. Animals can smell it for miles. Plants (such as they are) will defend it, with toxic sap, spines, , deep storage roots, tough bark, etc.
--if some rain comes on a regular cycle, you'll get lots of adaptations to respond to this. Wildflowers that germinate, bloom and go to seed in days. Animals that stay dormant for months, maybe years, then come rushing out when the rains fall. If the rains don't come regularly, then the life will be highly mobile, always wandering in search of where the rains fell. Probably lots of flying animals, and floating seeds.
--Compared to what we're used to, this could be a very lonely, empty place. Small populations huddled here and there, surrounded by vast open, lifeless flats. What does this mean for the culture? Also, water is really really precious. You might have "Dune"-esque water recycling (a man's body fluids are worth keeping)
--This ecology probably wouldn't support much in the way of your traditional big monster type things (unless you want it too. Then maybe add a bunch of inedible sea life). They can eat you, you can't eat them...).
--What do these people do for organic materials: rope, fabric, paper, oil? Import it from far away? Grow it in precious, carefully cultivated gardens? That would make it really valuable. Maybe you need the inedible sea life for skin and oils? Or maybe there are a few places where the rains do come regularly, if only for short time, and there are elaborate systems of catchments and cisterns for storage. This would change warfare too: water might be so precious that only the most desperate or depraved will smash structures. No wall-smashing, dam-bursting, well-poisoning. Much more emphasis on lighter, faster actions and raids (for that matter no heavy armor: too hot).