Nevus

Nevuses are a unique species. Like the other sentient species of the Overlord world, they originate elsewhere and so there must be a world in which they are common and not at all unusual. That is not the case in either the Overlord world or on Earth, because they are rather odd people when compared to the other species. In terms of balance, they tend to fall right between science and magic.
They have greenish skin, a tail like that of a horse, and two sets of arms. Beyond that, they are quite short and exceedingly nervous and paranoid. They originated in Sornevo, but they are now fairly evenly spread across the world. Nevuses are fairly nervous creatures that do not spend a great deal of time interacting with others if they can help it. As a race they are inclined toward pessimism and being anti-social. They are also inclined toward the medical sciences, and to professions that require attention to detail.
In the first hundred years or so after the disappearance, the nevuses were able to create artificial Portals to their homeworld, but then they stopped. It is unclear as to why they stopped trying to connect. In any case they are no longer able to create such portals, willingly or unwillingly.