This animate pile of mud seems barely able to maintain the semblance of a humanoid form made of dripping sludge. Not a true elemental like the earth elemental they can be found on the Elemental Plane of Earth.
Where the Plane of Earth borders the Plane of Water, a mixing of the fundamental elements occurs—it is in this borderland that the mud elementals dwell. Scorned by earth and water elementals, mud elementals usually look like vaguely recognizable blobs of mud in the shape of a Material Plane creature, whether a humanoid, an animal, or even an immense insect. The exact density of their muddy bodies varies—some might be composed of silty water, while others are thick, like river clay. Large and powerful mud elementals tend to have worm-like, reptilian, or frog-like forms.