Kobold (The Lost World)

The Cobalts are a subterranean race in the Lost World.

Physiology
The Cobalts dwell 50 miles below the Earth's surface in an area beneath the Plateau where the Earth's electromagnetic fields, created a pocket atmosphere and artificial light for habitable conditions. They are a subterranean species, with skin as solid as metal, capable of generating heat. They possess their own language resembling growls and clicks.

Cobalts evolved to withstand the immense pressure of the Earth's core, when they come closer to the surface they most generate a electromagnetic field to keep their bodies compressed otherwise they would explode. Interaction with sudden temperatures, hot or cold, cause them to expand and contract rendering them to pieces.

History
Lionel Holt, a head of the geologist department at Oxford University during the 20th century, postulated that these beings existed. However his theories were ridiculed by the scientific community forcing into self-exile. He eventually came to the Plateau where he discovered the Cobalts. After learning the Cobalt's advanced geo-dynamic sciences and their ambition to conquer the world, Lionel assisted them to have revenge on the world that spurned him. In order to devise a means for the Cobalts to safely emerge from the surface, he concocted a plan to bring his old friend Professor George, who was trapped on the Plateau to assist in building a uranium engine to create a magnetic field across the planet to safely allow the Cobalts to inhabit the surface.

Under the ruse of helping his friend for the rest of his party's safety, Challenger sabotaged the machine causing the machine to explode, collapsing the underground world of the Cobalts.

Culture
According to Lionel Holt, the Cobalts possess geological sciences way ahead of 20th century Earth.

Source

 * Lost World Under Pressure