Day 3. Working more into details and a bit of the land around the desert merms. The tectonic plates of the earth these mer live on are constantly shifting, which in turn causes the sands of the western searing cauldron to act more in itself like water - it's less rigid and flows like water.
While these mer did originally evolve from their ocean counterparts, their fish tails were never lost due to its necessity in the sand. Their front "fins" are more like seal flippers, they're flexible and strong, and can be used to prop up the creatures as well as be used as powerful rudders beneath the surface and will aid swimming "up stream" in the sand if they travel too far. Matriarchs can grow up to twice the size of an average mer if they are to live long enough and while each tribe are generally coexisting with each other, they won't tolerate territory infringement. A grand matriarch will serve as both a mystic leader and leader of the hunt!
Will work a bit more on the environments and some male mer tomorrow!