Explorers in a vast, dark subterranean cave with giant glowing roots, bioluminescent fungi, and a mysterious floating structure. Fantasy art.

A hollowed-out planet with an ecosystem and civilization thriving deep below the surface. This subterranean world is ancient, its technology long forgotten, and its inhabitants worship long-forgotten deities—the Old Gods. The world is slowly dying as its sun (an artificial light source) begins to flicker and fail. Mood/Atmosphere: Dark and oppressive, with a constant low hum from the failing artificial sun. The tunnels are ancient and winding, populated by strange, almost alien creatures. There’s a palpable sense of something ancient, powerful, and forgotten hiding beneath the surface. See more