Slyth

Slyths were a race of humanoid shapechangers of the Underdark who cared deeply for its environment and worked to ensure it was not defiled. Though not a populous race, the ooze-like denizens of the underground had a strong influence in the Night Below and made their presence felt in many ways over the course of their long lives.

Description
In their true forms, slyths were amorphous creatures somewhere between liquids and solids in consistency, resembling puddles of mud, syrup, or oil. They also possessed humanoid forms, appearing as bald humans of varied skin tones, with brown tones being the most common. Compared to humans they were slightly taller than the norm among that race, and had softer, more rounded features.