The Underplane

The Underplane is a subterranean region of Mythos. It exists as a system of interconnected caverns all over the world.


Many of the Underplane's inhabitants are descended from top-dwelling creatures, that became lost in the caves and gave up hope of ever returning home. Examples include the Cave Eagle and the Naked Mole Bear.

Other creatures are specially adapted to the area, using such adaptations as sonar and bioluminescence. Many mushrooms give off blue light, to attract insects to eat.

The region has few sapient inhabitants, but they exist. Sapient beings include the Kobolds and the Olm People.


The Underplane has existed for as long as there has been a Mythos.