Race: Mysterious Being

Age: Unknown

Gender: Unknown

Location: Under the earth's crust

Abilities: Immense Strength

Affiliation: Mother Earth

Debut: Chapter 4/Episode 1

The Subterranean People are the self-proclaimed "True People of the Earth". They are ruled by the Subterranean King and live under the earth's crust, but grew too numerous in numbers and planned to take over the surface.

(Source: One-Punch-Man Wikia)