Just quicksand
This mod introduces a dangerous type of sand - quicksand, which appears in desert biomes. Once trapped in such a trap, it will be very difficult for the player to escape on their own - rescue will require the help of water or the use of blocks.
The feature of quicksand is that it damages all creatures and objects that come into contact with it. This is a simple but effective modification that adds a new element of danger to desert locations.