Margian

Ethnicity of Vanadians that originate from the core and mantle of Vanadia. They live in a very large and complex labyrinth deep underground on the Vanadian homeworld. The race that seeded the vanadians built it originally, but using nanobot manipulating archaeotech provided to them also from the race that seeded them, margians managed to expand it.  To prevent the labyrinth from becoming extremely hot in contact with the magma of the mantle, it is insulated with Hardlight, with cooling systems installed. Heating any room is very easy, as a small amount of heat is taken from the mantle.
  Food has become expensive in the Margian labyrinth. They have no access to the surface. (In fact their existence was unknown to all of surface vanadian society until they invented a method to perform deep scans of Vanadia.) Another thing that the vanadian seeder race provided to margians just so they could survive is large farm areas featuring UV lights. The plants take energy from the lights. Due to the sheer size of these rooms, farms have become expensive to build.
  Due to the low gravity of the mantle and core, Margians have weaker bones than other vanadians. Margian bodies have adapted to underground conditions better.
  The margian people appear very different from other vanadians almost to the point of speciation. However, insufficient time has passed for them to speciate truly. Margians often appear larger than regular vanadians, with larger eyes to take in more light, and they have a slightly slower metabolism to conserve food. Far in the future, after having become a member of the HF faction, the technology that the vanadians could access increased significantly. This allowed the margians to excavate new tunnels and structures and construct their own rooms, allowing them to expand. Even further advances in technology allowed them to do this more quickly and safely, the latter of which being important because the mantle where these ancient structures were built is dangerously hot and there is a lot of ground pressure from above.
  Conflicts have happened and have led to the destruction of some rooms, despite the very strong shielding that every room was made out of. This collapse was impossible to repair until they obtained much more advanced HF technologies. Heat from the mantle would also often come through the seeps and cracks in shattered rooms, but the ancients who seeded the vanadian species took this into account. The rooms will slowly repair themselves over time and it would take a long time to make the entire mantle cities extremely hot.