Hardened lump of earth jutting out of the ground unnaturally, like a pimple. Located to the southwest of the Temple of Mozz in the dry desert beyond the rises that flank the structure. Someone with really good hearing (elf) can press their ear against the lump and hear bubbling water underneath its exterior.
If someone in your party is capable of dealing 12 or more damage in a single strike, they can "pop" the Lump with one blow. Otherwise it takes two turns of cutting away at it with shovels and picks to open it up. When burst, the lump releases a torrent of fresh drinking water captured beneath the earth. Once the water stops coming, there remains a wet tunnel which is a few miles long. This leads to the secret aquifer beneath the Temple of Mozz.
Triangular tooth marks along the walls hint at this being the work of a giant sandworm; but these marks are fake. In truth this tunnel was dug by exiled desert-dwelling tribes of Mozz to attempt to save some of their "heretical" kin from being given a cruel wet burial.