Limis

A species of goo like beings that exist in Xeros. A superstitious belief is that they bring ill omen and when found are usually killed on sight. They have the ability to transform into a humanoid form sometime around puberty. The form they chose is one they are stuck with transforming into for their entire life. If they choose to take the form of a human, elf, or tiefling, then that is the form they will always transform into, although some have taken to keeping the color aspect of the goo like form in their humanoid form through their hair, eyes, even skin color.
They are said to come from The Shadelands, adding more their mysterious nature, as what they were before coming to the material plane is completely unknown, even to the beings themselves. Some trauma has shaken their minds and erased what the were before and even what happened there.
Upon first arriving on the material plane, they were discriminated against and killed on sight, but they did have allies in the Drow and Moon Elves. Since they were already shunned as people, helping another outcast race was something they did not mind.
They are freely able to flip between their goo and humanoid forms at will and everything on their person will be sucked into their goo form, leaving them in a speedy and flexible state. They hide among communities as different races, some never being revealed and keeping that secret to their dying day, sometimes even to their loved ones. They can reproduce with any race and give birth to a child, but there is always a chance that they can give birth to another Limis.