In the most native of desert villages, those that are hidden amongst the sands in far away lands, they worship strange creatures that are primarily the plants that thrive in the heated dryness. These creatures, are Cactolems, guardian like beings made from cacti itself.

Despite the material, these guardians fiercely protect their helpless village kin, continue to provide them flowers, and act accordingly compared to an iron golem. Even though they are made of plants, they are just as tough as iron and pack a prickly punch, they do have a tendency to consume humans they are not protecting such as adventurers and illagers alike.

That would explain the large gaping mouth for a stomach and could also justify their toughness, and possibly why they exist in the first place...