I like these ideas and the work alot.
But I'd like to suggest something, if I may.
The "Dry" or "landbased" sand monsters are fine, but I'd like to see some more ideas for aquatic sand beasts.
Look up some sea creatures, there's plenty of existing sea creatures that live on the bottom on earth that would be absolutely terrifying to run into.
Sand worms give me the creeps.
(I'm asking this because the idea of playing the water breathing race and exploring interests me, as I think those could be the most interesting areas/ecologies).