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.
The babies of a small village has been disappearing lately, rumour has it that a demon living in the forest has taken them. The monster has the appearance of a shriveled old woman. A hag, disheveled, with maniacal appearance, wild-looking hair, and an oversized gaping mouth. Long pendelous breasts. The villagers say she eats the newborns and has sharp claws that are created for mangling. No one dears to challenge her, enter the PCs.