Waterseeker

The continent of Beraca is well known for the large expanses of desert that cover much of it. With most settlements dotted along the coast or by the sides of rivers there vast swathes of unclaimed land that present many challengers for travellers. Some of these challenges are very real while the existence of others is a little more dubious. One of the possibly fictional challenges is the waterseeker.
Waterseekers are reputed to be spirits which seek out water and turn it to sand. While some claim they exist others view them as an excuse used by those who haven't been rationing their water properly. Whatever the truth of the matter, various traditions have developed amongst the guides who help people cross the drier areas of the continent which are supposed to ward of the creatures.
Waterseekers resemble a cloud of sand, at least when destroying water. Those that claim to have seen one say that the sand seems to form itself into an indistinct face, or it may coalesce into a hand or arm. They are most commonly seen in sandstorms when groups of them form a fall of faces that seem to be crying out.

Circle in the sand

A circle drawn in the sand.
Drawn deep with tool not hand.

— Anonymous Guide

According to the guides a waterseeker does not like to cross areas that have sharp changes in height such as canyons and cliffs. A deeply drawn line in sand or dirt can help ward of a waterseeker. The circle can't be drawn by hand as if any moisture is left behind the waterseeker will be drawn down into the line and will then be able to reach your water as it emerges.

Salted Water

Waterseekers are also reputed to dislike water that has salt in it, which is one of the reasons they don't try to dry up the ocean. Many guides insist of adding salt to everyone's water bottles to reduce the chance of a waterseeker changing the contents to sand.

No you don;t have to add salt. You can always look for another guide instead

— Common guide statement

What is a Waterseeker?

There are several theories on what waterseekers are. One is that they are the spirits of those who died of thirst while travelling. Trapped in this world, desperately thirsty but unable to drink their efforts ti qunech their thirst end up destroying water. Each person that dies after having their water taken becomes a new waterseeker increasing the threat they present.
Another theory is that they are creations of a spellcaster leaving deep in the desert. The waterseekers hunt down water for this caster and instead of destroying it, transport the water to the caster's lair.