Desert market

Deep in the desert of the kingdom of the Elements lies a camp, more than a camp, a market for criminals and colorful characters.  The only way to get in is to know someone.  This camp was built entirely by sand blights who maintain it to this day.
Sand blights have a unique ability to tunnel under the sand.  Making them great thieves anywhere with sand.  they can move air and rock making sand their perfect element.  They are dangerous anywhere with sand, or even anywhere they bring sand.  They often will carry backpacks filled with sand with them everywhere they go.  Steal something, unzip the backpack, kick up a small sand storm, and by the time it is over, they are long gone with everything you own.
If the ground is made of sand, they steal something of yours, kick up a sand storm for a mere second and drop themselves into an underground tunnel they carve as they run, impossible to follow as their tunnel will collapse behind them at will.  In the case of the Desert Market, they have compacted sand to create tunnels underground of stone.  In a large cavern of their own design, which changes constantly, lies a market for thieves and criminals of every kind.  This cavern is encapsulated in sand which has been compressed to sandstone.  The whole market is in a long disk of sandstone which they keep underground in the sand of the desert.  They can move the disk through the sand so the market can be anywhere in the desert, and they always keep it moving. 
In most cases the market is on the move, only a sand spirit can get you in, by displacing the sand to drop you in.  Many people here roamers of this market, some believe in it, others aren't so sure, most can't prove it exists.  Sadly, it is another reason Sand Blights are seen as only ever criminals.