A dangerous, alien plane where glowing frog-slimes slither and slurp, metal-skinned bird people rebuff diplomacy, and only the endless subterranean tunnels are safe (just mind the gravity-bending moles). Visitors will have to skulk around in the dark to avoid the curse carried by the sunlight. Because (have I mentioned?) the sun is the source of a powerful curse--one that covers the whole planet.
Legends abound in some places about ancient landforms (Islands, Peninsulas, Mountains) that dissapeared long ago in towers of glowing energy. (See Any Unnatainable Glory entries for more info)