In the game Lunar: Silver Star Story Complete or it's PSP port/remake Lunar: Silver Star Harmony, there are 3 villains who are allies of the Vile Tribe. They are the 3 sisters - Xenobia, Royce, and Phacia - and they work under the Magic Emperor. By all accounts they are members of the Vile Tribe, but they are human. All other members of the Vile Tribe appear to be intelligent monsters. Why aren't the 3 sisters similarly monstrous in appearance?
The Vile Tribe "race" is actually a mixture of multiple races.
Unable to restore the planet until several millennia had passed, Althena instead chose to transform the planet's moon into an Earthlike world, and transported the survivors there. These included not only humans but also a race of "beast-men", and another race of elf-like beings skilled in wielding magic. They would later come to be known as "The Vile Tribe" after they rejected Althena's teachings. She was forced to banish them to an area of Lunar called "The Frontier," a barren wasteland where even Althena's magical power could not reach. They became enemies of Althena and her followers for thousands of years.