The City of Strangers. The Beautiful City. The City of Gold. The City of Sharks.
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.
Mondaloa is a name shared by both a city and a deity. Mondaloa, the city, is built on layers of crypts and tombs that are far more opulent and majestic than the city that covers them. Mondaloa, the deity, is the god of rest, peace, and death. There is nothing Mondaloa desires more than to see the dead buried deep in their tombs where they can rest in honor and peace. But there is trouble: something is torturing the dead of the city, and driving them to madness and rage. Now, 500 years of honored ancestors are trickling into the city above, seeking blood and pain and death.
As they travel they notice a horrible rotten smell. As they travel it gets stronger and stronger forcing them to cover their noses and mouth less they choke on the horrible smell. Stream full of dead fish. Spawning trout die in mass quantities after they spawn littering areas with dead fish dying and deteriorating in the sun.